Gun plot is flawed (6)
I believe the answer is:
pistol
'gun' is the definition.
(I know that pistol is a type of firearm)
'plot is flawed' is the wordplay.
'flawed' is an anagram indicator (I've seen this in other clues).
'plot'+'is'='plotis'
'plotis' anagrammed gives 'PISTOL'.
(Other definitions for pistol that I've seen before include "potential killer?" , "Type of gun" , "Arm" , "Spoilt these guns" , "making an appearance in Shakespeare's King Henry V" .)