Pillage with gun (5)
I believe the answer is:
rifle
I believe this clue is a double definition.
'pillage' is the first definition.
(I know that pillage can be written as rifle)
'gun' is the second definition.
(I know that rifle is a type of firearm)
'with' is the link.
(Other definitions for rifle that I've seen before include "Firearm - plunder" , "Long-barrelled gun" , "Shoulder firearm" , "Gun; thoroughly search" , "Shoulder weapon" .)