Nest item (3)
I believe the answer is:
egg
'nest item' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for egg that I've seen before include "Croque-madame ingredient" , "Food in a shell" , "Poacher's requisite" , "Cooked breakfast staple" , "Rasher to go with this" .)