FORM - 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule 13) A TEA PRODUCT HINDUSTAN UNILEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Unilever Limited, Unilever House, B.D. Sawant Marg, Chakala, Andheri (East), Mumbai - 400 099, Maharashtra, India The following specification particularly describes the invention and the manner in which it is to be performed. TECHNICAL FIELD The present invention relates to a tea composition- More particularly the present invention relates to a black tea composition and a process to prepare the same. BACKGROUND AND PRIOR ART Tea is a very popular beverage which is consumed throughout the world. Of the various tea products, black tea is more popular. Black tea manufacture involves the following steps : (i) withering of fresh leaves of the plant Camellia sinensis, which typically involves allowing plucked tea leaves to lose moisture in a shallow trough where biochemical reactions occur causing; formation of many beneficial compounds including aroma compounds; (ii) maceration of the withered leaves which is a process where the tea cellular structure is broken which causes further biochemical reaction to occur; (iii) fermentation of the macerated leaves during which enzymes in the tea leaf use atmospheric oxygen to oxidise various substrates to produce coloured substances; and (iv) drying of the fermented leaves at high temperatures to stop the enzyme activity and bring down the moisture to less than 8 to 10% to produce the black tea. The black tea may then be sieved to the desired size range. The bigger sizes are preferred by the consumer. The finer grades are high in fibre and are considered as nearly waste material and fetch only a low price. Other tea products include green tea which is produced by the same process as for black tea except that the macerated leaves are not fermented. Partial fermentation is used to produce intermediate-type tea known as "oolong" tea. Green, black and oolong tea are products which are brewed in hot water to produce tea infusions wherefrom the tea leaf insolubles are filtered before the infusion is consumed. Sensorials of the tea products vary from one another. People have tried to add different additives (tea based or non-tea based) to enhance the taste, flavour or other properties of tea compositions. Indian patent Application 1750/MUM/2007 (Hindustan Unilever Limited, 2007) discloses a fortified tea composition comprising 30-95% black tea, 0.05-30% chicory, 0.5-40% binder and 0.01-5% micronutrient selected from a vitamin, calcium, zinc, iron or a combination thereof. The form of chicory used in 1750/MUM/2007 is chicory powder. Tea with added micronutrients increases the cost of the tea composition. This application teaches the addition of chicory to solve the problem of increased cost by using a combination of tea and chicory powder, which is believed to provide a beverage having the organoleptic properties and the appearance of regular black tea. EP1092349 (Unilever, 2001) discloses a tea product comprising 15- 95% by weight black tea, up to 5% of a mixture comprising fructose and glucose, and up to 5% of roasted nut powder. It is disclosed that the tea product further comprises roasted chicory, a flavouring agent, a dairy or non dairy whitener, starch, or a preservative. There is further disclosed a method for preparing a tea product with enhanced aroma and flavour comprising granulating 15-95% by weight black tea and mixing with it up to 5% of a mixture comprising fructose and glucose and up to 5% of roasted nut powder. The particle size of the granulated tea product is said to be in the range 0.5-5 mm. Though the added materials with the tea in the prior art add value or other sensorial properties to the end cup and make it cost-effective, most of the time we have found that they generate residue in the end cup. This residue is not preferred by the consumers. Due to this residue consumers often do not consume the tea beverage fully, rather waste nearly one-fourth of the cup. As a result there is wastage of tea beverage from each cup. Furthermore, granulation, which involves processing complexity and also requires addition of binding agents for granulation, affects the organoleptic properties of tea. Therefore there is a need to develop a tea product comprising different additives, which is substantially free from residue in the end cup thereby satisfying the consumers preference and reduce the wastage of end cup tea beverage and also which does not involve granulation, and hence processing complexity. OBJECT OF THE INVENTION In view of the foregoing it is an object of the present invention to provide a black tea product with additives which is substantially free from residue when reconstituted into a beverage. It is another object of the invention to provide a process for making a tea product with value added additives which does not involve granulation. The present inventors have surprisingly found that chicory granules of a specific particle size range when added to tea leaf ameliorate the problems relating to residue formation in the end-cup and/or allow for a simpler process which does not have the complexity of a granulation process and/or does not require the presence of further additives. SUMMARY OF THE INVENTION According to a first aspect the present invention provides a tea composition comprising: a) 50 to 99.5 % by weight of black tea; and b) 0.5 to 50 % by weight of chicory granules wherein at least 90% by weight of the chicory granules have a particle size in the range of 600 microns to 2000 microns. According to a second aspect the present invention provides a process to prepare a tea composition comprising the steps of: a) providing chicory granules in the size range of 600 microns to 2000 microns, b) mixing black tea with the chicory granules of step (a). The term "comprising" is meant not to be limiting to any subsequently stated elements but rather to encompass non-specified elements of major or minor functional importance. In other words the listed steps, elements or options need not be exhaustive. Whenever the words "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word "about". It should be noted that in specifying any range of concentration or amount, any particular upper concentration can be associated with any particular lower concentration or amount. The terms weight percent, percent by weight, % by weight, wt%, and the like are synonyms that refer to the concentration of a substance as the weight of that substance divided by the weight of the composition and multiplied by 100. The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to a composition containing "a compound" includes a mixture of two or more compounds. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments. DETAILED DESCRIPTION OF THE INVENTION "Tea" for the purposes of the present invention means tea material from Camellia sinensis var. sinensis and/or Camellia sinensis var. assamica. Especially preferred is material from var. assamica as this has a higher level of tea actives than var. sinensis. "Leaf tea" for the purposes of this invention means a tea product that contains tea leaves and/or stem in an un-infused form, and that has been dried to a moisture content of less than 30% by weight, having at least 90 wt% of the tea particles in the size range of 850 microns to 2000 microns. In other words 90% of the tea particles having a particle size of -8+18 mesh expressed in BSS mesh size scale where "+" before the sieve mesh indicate the particles are retained by the sieve and "-" before the sieve mesh indicates the particles pass through the sieve. "Fanning tea" for the purposes of this invention means a tea product that contains tea leaves and/or stem in an un-infused form, and that has been dried to a moisture content of less than 30% by weight, having at least 90 wt% of the tea particles in the size range of 600 microns to 1000 microns (particle size of -16+25 mesh). "Dust tea" for the purposes of this invention means a tea product that contains tea leaves and/or stem in an un-infused form, and that has been dried to a moisture content of less than 30% by weight, having at least 90 wt% of the tea particles in the size range of 250 microns to 600 microns (particle size of -25+60 mesh). The present invention provides a tea composition having 50 to 99.5 % by weight of black tea and 0.5 to 50 % by weight of chicory granules wherein at least 90% by weight of the chicory granules have a particle size in the range of 600 microns to 2000 microns (particle size of -8+25 mesh). Black Tea Black tea quality depends on the geographical origin of the tea. The tea composition of the present invention may have black tea made from any raw material that is tea leaf, fanning or dust tea and from any origin. The black tea is present at 50% to 99.5%, preferably 60% to 99.5%, more preferably from 70% to 99.5%, further more preferably from 80% to 99.5 by weight of the tea composition. It is most preferred that the black tea is present in an amount of 90% to 97% by weight of the tea composition. The black tea composition of the invention is such that preferably at least 90%, more preferably at least 92% and further more preferably from 95 to 100% by weight of the black tea has a particle size in the range of 250 microns to 2000 microns (particle of -8+60 mesh),. In a preferable embodiment the black tea composition of the invention is such that at least 90% more preferably from 95-100% by weight of the black tea has particle size in the range of 250 microns to 600 microns (particle size of -25+60 mesh). In another preferable embodiment the black tea composition of the invention is such that at least 90% more preferably from 95-100% by weight of the black tea has particle size in the range of 600 microns to 1000 microns (particle size of -16+25 mesh). Chicory granules Chicory is an essential ingredient of the tea composition of the present invention. Chicory is a flowering plant of the genus Chichohum of the family Asteraceae. Many species of chicory are known. It is grown in most continents including Europe, North and South America. The roots are roasted and grounded to prepare chicory granules and powder of different sizes. It is preferred that the chicory is roasted. Roasting of the chicory granules can be light, medium or dark as known by one skilled in the art. The most preferred is the medium roasted chicory. Preparation of the medium roasted chicory typically involves the following process steps: a) dicing the chicory roots in a dicer into cubes of preferably 1 to 2 cm length and (b) roasting the diced chicory roots in a chicory roaster. The degree of roasting depends on the time of roasting and heat input to the roaster. The roasting time is preferably from 60 minutes to 120 minutes. The preferred roasting temperature is from 90°C to 180°C. The chicory granules are present in 0.5% to 50%, preferably from 0.5% to 40%, more preferably from 3% to 30% by weight of the tea composition. The most preferred range is from 3% to 10% of the tea composition. The particle size distribution of the chicory granules is preferably such that at least 90% preferably at least 92% more preferably at least 95% and most preferably at least 99% by weight of chicory granules has a particle size from 600 microns to 2000 microns (particle size of -8+25 mesh). The tea composition may also preferably comprise at least 90% more preferably at least 92% further more preferably at least 95% and most preferably from 99 to 100% by weight of the chicory granules that have a particle size in the range of 600 microns to 1400 microns (particle size of-12+25 mesh). Alternately the chicory granules have particles in the size range of 1400 microns to 2000 microns (particle size of -8+12 mesh). The tea composition may also preferably comprise at least 90% more preferably at least 92% further more preferably at least 95% and most preferably from 99 to 100% by weight of the chicory granules having a particle size in the range of 1400 microns to 2000 microns (particle size of -8+12 mesh). Preferably the bulk density of the chicory granules is in the range of 380 to 450 g/L. More preferable the bulk density is 400 to 430 g/L. The tea composition optionally comprises other additives like Vitamins, minerals etc. However in one embodiment no further additives are required and the tea composition consists essentially of the black tea and the chicory granules. Process of preparing the tea composition The present invention also provides a process for producing the tea product comprising the steps of: a) providng chicory granules in the size range of 600 microns to 2000 microns, b) mixing black tea with the chicory granules of step (a). Details of the preferred process steps are given below. Preferably, chiocory granules in the desired size range are obtained by sieving chicory granules of different sizes. First, the chicory granules obtained after roasting and grinding are passed through a series of sieves. The sieving can be achieved in any convenient manner. However for the purposes of analysing size ranges, sieve analysis is conducted by Tyler Sieve analysis. In the Tyler Siever method meshes of different sizes are given different numbers termed as the BSS Number. All the sieve sizes mentioned in this application are expressed in the BSS mesh size. A minimum of two meshes of different mesh sizes are taken. The meshes are arranged in descending order of size. Chicory is placed on the upper mesh. The meshes along with the chicory are then placed inside a sieve shaker. The sieve shaker is switched on and operated till there are almost no more particles passing through the mesh. The amount of sample collected on the sieve is weighed and recorded. Chicory particles passing through the sieve with mesh size of 600 microns (BSS mesh No. 25) are termed as chicory powder and having particle size less than 600 microns. Chicory granules that pass through the sieve with mesh size of 1400 microns (BSS mesh No. 12) and are retained on the sieve with mesh size of 600 microns (BSS mesh No. 25) have a size in the range of 600 to 1400 microns and are referred to herein as Size 1 (particle size of-12+25 mesh). Chicory granules that pass through the sieve with mesh size of 2000 microns (BSS mesh No. 8) and are retained on the sieve with mesh size of 1400 microns (BSS mesh No. 12) have a size in the range of 1400 to 2000 microns and are referred herein as Size 2 (particle size of-8+12 mesh). After that the chicory granules within the size range of 600 microns to 2000 microns (particle size of -8+25 mesh) are selected after sieve analysis. The desired amount of chicory granules is weighed. Then the black tea is mixed with the chicory granules of desired size in a mixer. A high shear or a low shear mixer may be used for this purpose. Some examples of suitable mixers include Nauta, sigma, paddle, ribbon and Hobart mixers. Preferably the mixing is carried out for 15 to 30 minutes, most preferably for 15 minutes. A preferred mode of mixing involves addition of half the weight of the chicory granules followed by addition of half the weight of the black tea and then adding the remaining black tea followed by chicory granules in layers. EXAMPLES The invention will now be illustrated by the following non-limiting examples. Preparation of different tea compositions Different types of tea composition, both inside the scope of the invention and outside the scope of the invention were prepared as shown in Table 1. The tea used for preparing the compositions was a mixture of tea collected from southern and northern India. Tea compositions were made using tea leaf, tea fanning and dust tea. The leaf tea used for this purpose had a particle size of -8+18 mesh. The size of the fanning tea was -16+25 mesh and the size of the dust tea was -25+60 mesh. All mesh sizes were measured on the BSS mesh scale. Table 1 Example Tea leaf (wt%) Tea fanning