Damaged gun's alright internally (6)
I believe the answer is:
broken
'damaged' is the definition.
(synonyms)
'gun's alright internally' is the wordplay.
'gun' becomes 'bren' (Bren is an example).
'alright' becomes 'OK' (synonyms).
'internally' indicates putting letters inside.
'bren' enclosing 'ok' is 'BROKEN'.
(Other definitions for broken that I've seen before include "Defective" , "Smashed or tamed" , "Interrupted; inoperative" , "If it's not ..., don't fix it" , "Busted, damaged" .)