Drink sample (3)
I believe the answer is:
sip
'drink sample' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sip that I've seen before include "Take small mouthfuls of (drink)" , "Thimbleful" , "Drink daintily" , "Take a little of a drink" , "Drink gingerly" .)