Flan ingredients (4)
I believe the answer is:
eggs
'flan ingredients' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eggs that I've seen before include "Bacon and - -" , "Ova" , "Reproductive cells" , "Those scrambled, boiled, poached or fried" , "Contents of nests" .)