Sack and what may be put in it (7)
I believe the answer is:
plunder
'sack' is the definition.
(I know that plunder is a type of sack)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for plunder that I've seen before include "Loot" , "Stolen or looted goods" , "Sack - or what might be put in one!" , "Goods taken" , "Rob" .)