Bird that returns in winter generally (5)
I believe the answer is:
'bird' is the definition.
(egret is a kind of bird)
'returns in winter generally' is the wordplay.
'returns' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'terge' is hidden within 'winter generally'.
'terge' reversed gives 'EGRET'.
'that' is the link.
(Other definitions for egret that I've seen before include "flier" , "Stork-like bird" , "Greet (anag) -- wading bird" , "Heron-like wader" , "White-feathered wading bird" .)