Unfinished drink to swallow? (6)

I believe the answer is:

martin

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'swallow?' is the definition.
(martin is a kind of swallow)

I don't understand the remainder of the clue.

(Other definitions for martin that I've seen before include "Perhaps Dean" , "Bird of the swallow family" , "-- Chuzzlewit (Dickens)" , "Variety of swallow" , "25 across [CRANE]" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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