Sea-horse? (3)

I believe the answer is:

bay

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'horse?' is the definition.
(bay is a kind of horse)

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

(Other definitions for bay that I've seen before include "Sea inlet" , "Howl" , "Small alcove" , "laurel maybe" , "Inlet; shrub" .)

I've seen this clue in the Evening Standard.

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