Article turning his gun into pain (7)
I believe the answer is:
anguish
'pain' is the definition.
(anguish is pain or suffering)
'article turning his gun' is the wordplay.
'article' becomes 'a' (the indefinite article in English).
'turning' indicates an anagram.
'his'+'gun'='hisgun'
'hisgun' with letters rearranged gives 'nguish'.
'a'+'nguish'='ANGUISH'
'into' is the link.
(Other definitions for anguish that I've seen before include "Severe mental suffering" , "torture" , "Grief" , "Great sorrow" , "Severe mental distress" .)