Touch loud fish (4)
I believe the answer is:
'touch' is the definition.
(I know that feel is a more specific form of the action touch)
'loud fish' is the wordplay.
'loud' becomes 'f' (short for forte - 'loud' in music).
'fish' becomes 'eel' (eel is a type of fish).
(Other definitions for feel that I've seen before include "Have a belief; touch" , "Consider" , "Experience, perceive" , "Have sensation of" , "Fondle" .)