Old-fashioned, like unfermented grape juice? (5)

I believe the answer is:

musty

This clue is a double definition.

'old-fashioned' is the first definition.
(thesaurus)

'like unfermented grape juice?' is the second definition.
(must is grape juice before fermentation)

(Other definitions for musty that I've seen before include "Frowsty" , "Smelling of mould" , "Mouldy; outdated" , "Stale and dank" , "Mouldy; stale-smelling" .)

I've seen this clue in The Guardian.

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