Stabilising structure beneath a ship (4)

I believe the answer is:

keel

(Other definitions for keel that I've seen before include "Beam on the hull of a vessel" , "Longitudinal structure supporting the frame of a vessel" , "Part of ship's frame" , "Ship's basic longitudinal structure" , "Lengthwise structure of a ship" .)

I've seen this clue in The Times.

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