It has a yolk (3)
I believe the answer is:
egg
'it has a yolk' 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 "Cooked breakfast staple" , "Urge (someone on )" , "nit? Just a bit!" , "Breakfast food, perhaps" , "Quiche ingredient" .)