Join Red Army, even late at night (3,2)

I believe the answer is:

one am

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'late at night' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'join red army even' is the wordplay.
'even' indicates alternate letters (letters in even-numbered positions are used).
'join'+'red'+'army'='joinredarmy'
The alternate letters of 'joinredarmy' are 'ONE AM'.

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I've seen this clue in the Sydney Morning Herald.

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