Defective machine-gun all right inside (6)
I believe the answer is:
broken
'defective' is the definition.
(I've seen this before)
'machine-gun all right inside' is the wordplay.
'machine-gun' becomes 'bren' (I've seen this before).
'all right' becomes 'ok' (synonyms).
'inside' indicates putting letters inside.
'bren' enclosing 'ok' is 'BROKEN'.
(Other definitions for broken that I've seen before include "Bust" , "no longer working?" , "faulty" , "Smashed or tamed" , "Interrupted; smashed" .)