Somehow pistol is ruined (6)
I believe the answer is:
spoilt
'is ruined' is the definition.
(thesaurus)
'somehow pistol' is the wordplay.
'somehow' indicates anagramming the letters.
'pistol' anagrammed gives 'SPOILT'.
(Other definitions for spoilt that I've seen before include "Overindulged" , "Made a mess of" , "Harmed" , "messed up" , "Indulged" .)