Swimmer turned amber (5)
I believe the answer is:
bream
'swimmer' is the definition.
(bream is a kind of fish)
'turned amber' is the wordplay.
'turned' indicates anagramming the letters.
'amber' is an anagram of 'BREAM'.
(Other definitions for bream that I've seen before include "Broad, thin fish" , "River fish" , "Fish - English guitarist" , "Amber (anag) - fish" , "Fish of the carp family" .)