Get rid of plunder (4)
I believe the answer is:
sack
This clue is a double definition.
'get rid of' is the first definition.
(I've seen this before)
'plunder' is the second definition.
(synonyms)
(Other definitions for sack that I've seen before include "Dismiss (from a job)" , "See 12" , "Big, coarse bag" , "Plundering by a mob" , "It carries coal" .)