Fish that may be amber (5)
I believe the answer is:
bream
'fish' is the definition.
(type of fish)
'may be amber' is the wordplay.
'may be' is an anagram indicator.
'amber' is an anagram of 'BREAM'.
'that' is the link.
(Other definitions for bream that I've seen before include "River fish" , "Amber kind of fish" , "Food fish" , "Fish found in amber" , "Broad, thin fish" .)