Tavern serving (4)
I believe the answer is:
beer
'tavern serving' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for beer that I've seen before include "... this at pub?" , "pint" , "Hop-flavoured drink" , "Hopped drink" , "Drink using hops, malt, etc" .)