One or many men, maybe (4)

I believe the answer is:

unit

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'one' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

(Other definitions for unit that I've seen before include "Single element; one" , "Kitchen fitting" , "Specialised group" , "1 entity" , "Building block - small military force" .)

I've seen this clue in the Evening Standard.

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