River adopted by ray — and another fish (5)
I believe the answer is:
bream
'fish' is the definition.
(type of fish)
'river adopted by ray' is the wordplay.
'river' becomes 'r' (abbreviation).
'adopted by' means one lot of letters goes inside another (I've seen this in other clues).
'ray' becomes 'beam' (synonyms).
'r' placed within 'beam' is 'BREAM'.
'and another' is the link.
(Other definitions for bream that I've seen before include "Food fish" , "Broad, thin fish" , "Edible fish" , "Bar me from the freshwater fish" , "River fish" .)