Rejected fish unacceptable for stew (6)
I believe the answer is:
ragout
'stew' is the definition.
(ragout is a kind of stew)
'rejected fish unacceptable' is the wordplay.
'rejected' says the letters should be written backwards.
'fish' becomes 'gar' (gar is a kind of fish).
'unacceptable' becomes 'out' (I've seen this in other clues).
'gar' backwards is 'rag'.
'rag'+'out'='RAGOUT'
'for' is the link.
(Other definitions for ragout that I've seen before include "Highly-seasoned stew" , "Highly seasoned meat and vegetable stew" , "Temper showing? No, it's a stew" , "Stewed meat/veg dish" , "Spicy dish" .)