A sack (3)
I believe the answer is:
bag
'a sack' is the definition.
(I know that Bag is a type of sack)
This is the entire clue.
(Other definitions for bag that I've seen before include "Secure" , "Quantity of game shot in a particular period" , "Item of luggage; catch and kill (an animal)" , "Container for holding or carrying" , "Claim" .)