Young child’s drink (3)
I believe the answer is:
tot
I believe this clue is a double definition.
'young child's' is the first definition.
(I've seen this before)
'drink' is the second definition.
(I've seen this before)
(Other definitions for tot that I've seen before include "two fingers, perhaps" , "slug?" , "Youngster; short drink" , "Nip" , "Add up, aggregate" .)