Frittata ingredient (3)
I believe the answer is:
egg
'frittata ingredient' 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 "Spur" , "Curate's good in parts" , "Thin-shelled reproductive body" , "Urge (someone on )" , "Over-easy breakfast item?" .)