Food, say, ending in dressing (3)
I believe the answer is:
egg
'food' is the definition.
(egg is a kind of food)
'say ending in dressing' is the wordplay.
'say' becomes 'eg' (both can mean 'for example').
'ending in' says to take the final letters.
The final letter of 'dressing' is 'g'.
'eg'+'g'='EGG'
(Other definitions for egg that I've seen before include "Mine (slang)" , "Yolk and white in a shell" , "Curate's good in parts" , "Bomb or mine (sl.)" , "Reproductive cell" .)