A small drink for a small child (3)
I believe the answer is:
tot
I believe this is a double definition.
'a small drink' is the first definition.
(I've seen this in another clue)
'small child' is the second definition.
(tot can mean a baby or toddler)
'for a' acts as a link.
(Other definitions for tot that I've seen before include "Spirit measure" , "Sum for the little one" , "Add up like infant" , "Drop" , "Add up for baby" .)