Join in less than a minute, maybe (5)

I believe the answer is:

unite

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'join in' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for unite that I've seen before include "Combine - join" , "Marry" , "fuse" , "Join together, merge" , "Make one" .)

I've seen this clue in the Evening Standard.

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