Badly damaged, a gun is out for good (6)
I believe the answer is:
broken
'badly damaged' is the definition.
'broken' can be an answer for 'damaged' (associated in meaning). I'm not sure about the 'badly' bit.
'a gun is out for good' is the wordplay.
I cannot quite understand how this works, but
'good' could be 'ok' and 'ok' is found in the answer.
'gun' could be 'bren' (Bren is an example) and 'bren' is present in the remaining letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for broken that I've seen before include "Busted, damaged" , "Shattered, perhaps emotionally" , "no longer working?" , "Interrupted; smashed" , "Interrupted; inoperative" .)