Dismiss member with pistol, say (7)
I believe the answer is:
firearm
'pistol say' is the definition.
(pistol is a kind of firearm)
'dismiss member' is the wordplay.
'dismiss' becomes 'fire' ('fire' can be a synonym of 'dismiss').
'member' becomes 'arm' (arm is a kind of member).
'fire'+'arm'='FIREARM'
'with' is the link.
(Other definitions for firearm that I've seen before include "Colt possibly" , "One's fired" , "dangerous weapon" , "Rod" , "piece" .)