Back of a boat (5)
I believe the answer is:
stern
'back of a boat' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stern that I've seen before include "Austere rear part of a ship?" , "Rear end" , "Rear of a vessel" , "Unyielding part of the ship" , "Tail of a beagle" .)