An angler might handle this river fish (4)
I believe the answer is:
reel
'an angler might handle this' is the definition.
The definition suggests a singular noun which matches the answer.
'river fish' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'fish' becomes 'eel' (eel is a type of fish).
'r'+'eel'='REEL'
Can you help me to learn more?
(Other definitions for reel that I've seen before include "Drum - dance - music" , "Dance - sway - cotton holder" , "Film spool" , "Turn around in the dance" , "Stagger with rod winder" .)