Small drinks small child returns (4)
I believe the answer is:
tots
'small drinks' is the definition.
'small child returns' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'child' becomes 'tot' (I've seen this before**).
'returns' says the letters should be written in reverse.
's'+'tot'='stot'
'stot' in reverse letter order is 'TOTS'.
(Other definitions for tots that I've seen before include "Party drinks" , "Sailors' drams" , "Adds up like small children" , "Little drinks" , "Young children - shorts" .)