Bird-to-be (3)
I believe the answer is:
egg
'bird-to-be' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for egg that I've seen before include "Food in a shell" , "One beaten by a whisker perhaps" , "Good, boiled, yoke or head" , "Item of food" , "Reproductive part" .)