The floating wreckage of a ship (7)
I believe the answer is:
flotsam
'the floating wreckage of a ship' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for flotsam that I've seen before include "Things found floating from a ship" , "Goods lost" , "Detritus" , "Wreckage found floating" , "Vagrants" .)