Cola formula, almost pure drink (7)
I believe the answer is:
alcohol
'drink' is the definition.
(alcohol is a kind of drink)
'cola formula almost pure' is the wordplay.
'formula' is an anagram indicator (the letters are the ingredients or formula).
'almost' means to remove the last letter (most of the word but not all of it).
'pure' becomes 'holy'.
'holy' with its final letter taken off is 'hol'.
'cola' is an anagram of 'alco'.
'alco'+'hol'='ALCOHOL'
(Other definitions for alcohol that I've seen before include "lager, perhaps" , "Spirits etc" , "solvent" , "wine, say" , "The intoxicant in drink" .)