Duct (4)

I think it could be either:

pipe

tube

'duct' is the definition.
(thesaurus)

This is the entire clue.

(Other definitions for pipe that I've seen before include "Water carrier" , "Wine cask; sing shrilly" , "Something in the organ loft" , "Whistle" , "Tube; wind instrument" .)

I've seen this clue in The Washington Post Sunday and the Evening Standard.

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