Nought's amiss with weapon (7)
I believe the answer is:
shotgun
'weapon' is the definition.
(shotgun is a kind of weapon)
'nought's amiss' is the wordplay.
'amiss' indicates an anagram.
'noughts' with letters rearranged gives 'SHOTGUN'.
'with' is the link.
(Other definitions for shotgun that I've seen before include "piece" , "Smooth-bore weapon" , "Type of wedding - weapon" , "Hunting firearm" , "Noughts (anag) - type of wedding" .)