Discarded cargo (6)
I believe the answer is:
jetsam
'discarded cargo' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for jetsam that I've seen before include "Unwanted material thrown overboard" , "Items thrown overboard" , "Goods jettisoned from a ship and washed up on shore" , "Ship's cargo thrown overboard" , "Things thrown overboard and washed up ashore" .)