Grain, as used to make a drink (7)
I believe the answer is:
sangria
'a drink' is the definition.
(type of alcoholic drink)
'grain as used' is the wordplay.
'used' indicates an anagram.
'grain'+'as'='grainas'
'grainas' is an anagram of 'SANGRIA'.
'to make' acts as a link.
(Other definitions for sangria that I've seen before include "Spanish drink of red wine with soda water or lemonade" , "Spanish drink based on red wine" , "A party drink" , "Spanish drink of red wine and spices" , "Spanish drink of wine, lemonade, fruit, etc" .)