Twin-hulled craft (9)
I believe the answer is:
catamaran
'twin-hulled craft' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for catamaran that I've seen before include "Two-hulled boat" , "Boat with twin, parallel hulls" , "raft of logs" , "Boat with two hulls" , "One vessel" .)