Grim end to a boat (5)

I believe the answer is:

stern

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'grim' is the definition.
(I know that grim can be written as stern)

I can't explain the remainder of the clue.

(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" .)

I've seen this clue in The Globe and Mail.

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