Reportedly overprotecting young fish (7)
I believe the answer is:
codling
'young fish' is the definition.
(young cod)
'reportedly overprotecting' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'overprotecting' becomes 'coddling' (as in mollycoddling).
'coddling' is a homophone of 'CODLING'.
(Other definitions for codling that I've seen before include "One apple" , "little one underwater?" , "Small fish" , "Immature fish" , "kind of apple" .)