Turn goes badly for swimmer (8)
I believe the answer is:
sturgeon
'swimmer' is the definition.
(type of fish)
'turn goes badly' is the wordplay.
'badly' indicates an anagram (letters in the wrong order).
'turn'+'goes'='turngoes'
'turngoes' anagrammed gives 'STURGEON'.
'for' is the link.
(Other definitions for sturgeon that I've seen before include "Our gents caught a large fish" , "Our gents, oddly, caught the fish" , "Fish sought for caviar" , "Fish providing isinglass" , "So urgent to find caviare-bearing fish" .)