A bit of a creature with egg hatching out (3)
I believe the answer is:
tad
'a bit' is the definition.
(both can mean a small amount)
I cannot understand how the rest of the clue works.
(Other definitions for tad that I've seen before include "Small amount or degree" , "A small amount (colloq.)" , "Little bit" , "Modest amount" , "little boy" .)