Drink at bedtime (8)
I believe the answer is:
nightcap
'drink at bedtime' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for nightcap that I've seen before include "A drink before bed, probably alcoholic" , "Head covering" , "something you get at the eleventh hour?" , "Last drink of the day?" , "Old headgear" .)