Drink some sip in tavern (4)
I believe the answer is:
pint
'drink' is the definition.
(eg a pint of beer)
'some sip in tavern' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'PINT' is hidden in the letters of 'sip in tavern'.
(Other definitions for pint that I've seen before include "Measure of the plain man's alcoholic drink" , "Half a quart" , "Unit of capacity" , "Liquid measure" , "Liquid meassure - four gills" .)