Ray’s about right for fish (5)
I believe the answer is:
bream
'fish' is the definition.
(bream is a kind of fish)
'ray's about right' is the wordplay.
'ray' becomes 'beam' (synonyms).
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'beam' placed around 'r' is 'BREAM'.
'for' acts as a link.
(Other definitions for bream that I've seen before include "Bar me from the freshwater fish" , "Carp relative" , "River fish" , "Broad, thin fish" , "Fish - English guitarist" .)