In the bottleneck in the port (4)

I believe the answer is:

cork

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

I don't understand the rest of the clue.

(Other definitions for cork that I've seen before include "Irish seaport" , "Bottle-stopper for a southern city" , "Tree bark from the South of Ireland?" , "It's needed for a bottle of wine" , "Tree used in bottling" .)

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

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