Firm with smoking gun? Fit with a silencer? (10)
I believe the answer is:
soundproof
'firm' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?
'smoking gun? fit with a silencer?' is the wordplay.
I cannot really see how this works, but
'fit' could be 'sound' (associated in meaning) and 'sound' is present in the answer.
'smoking gun?' could be 'proof' (I've seen this in another clue) and 'proof' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'with' is the link.
Can you help me to learn more?
(Other definitions for soundproof that I've seen before include "Such a quiet room" , "intended to stop hearing" , "suitable for concerts?" , "Bar racket" , "keeping the racket inside?" .)