Main body of a ship (4)
I believe the answer is:
hull
'main body of a ship' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hull that I've seen before include "Frame of a ship" , "Framework of ship" , "Humber port - ship's frame" , "Main body of ship" , "Main body of vessel" .)