Beetles lose risky bet with fish (4)
I believe the answer is:
eels
'fish' is the definition.
(eel is a type of fish)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for eels that I've seen before include "Slithery fish" , "They have long bodies and very small fins" , "Fish (that may be jellied)" , "Abstract nineteen sixties style" , "Else they're fish" .)