Wreck a danger at sea (7)

I believe the answer is:

torpedo

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'wreck' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for torpedo that I've seen before include "Sea-borne missile" , "Explosive missile from submarine" , "Missile form a submarine" , "Naval weapon" , "ruin" .)

I've seen this clue in The Sun.

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