Small boy devouring a cold dish (5)
I believe the answer is:
salad
'cold dish' is the definition.
(I've seen this before)
'small boy devouring a' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'boy' becomes 'lad' (lad is a kind of boy**).
'devouring' means one lot of letters goes inside another.
's'+'lad'='slad'
'slad' placed around 'a' is 'SALAD'.
(Other definitions for salad that I've seen before include "See 22" , "A dish of lettuce and vegetables" , "Cold dish of raw vegetables" , "One that may be dressed for dinner" , "Mainly raw cold dish" .)