Plunders for guns (6)
I believe the answer is:
rifles
I believe this is a double definition.
'plunders' is the first definition.
(I know this)
'for guns' is the second definition.
(rifle is a kind of gun)
(Other definitions for rifles that I've seen before include "Searches and robs, using longbarreled gun?" , "Weapons; searches through" , "Shoulder firearms" .)