Fish bit angler's bottom - what cheek! (5)
I believe the answer is:
brass
'cheek' is the definition.
(brass neck can mean cheek or insolence)
'fish bit angler's bottom what' is the wordplay.
I cannot quite see how this works, but
'bottom' could be 'ass' (synonyms) and 'ass' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for brass that I've seen before include "Front" , "Impertinence" , "Alloy of copper and zinc" , "Zinc-copper alloy - cheek" , "Ready" .)