United to shut taxi areas (6,5)

I believe the answer is:

closed ranks

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'taxi areas' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'united to shut' is the wordplay.
'united' is a charade indicator (letters next to each other).
'to' becomes 'closed' (I've seen this before).
'shut' becomes 'ranks' (I can't explain this - if you can you should give a lot more credence to this answer).
'closed' next to 'ranks' is 'CLOSED RANKS'.

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

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