Grim end to a boat (5)
I believe the answer is:
stern
'grim' is the definition.
(I know that grim can be written as stern)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stern that I've seen before include "Rear; severe, serious" , "Severe in the rear of the ship?" , "Stiff - back - not smiling" , "Strict, grimly serious" , "Unyielding - rump" .)