Haddock relative
I believe the answer is:
cod
'haddock relative' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cod that I've seen before include "Pay when you get the goods - sounds fishy" , "A foolish sort of a fish" , "Initially, pay when you get the goods" , "A fool of a fish" , "Edible fish" .)