Urban district contained within barrier it has (5)

I believe the answer is:

erith

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'urban district contained' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'within barrier it has' is the wordplay.
'within' indicates a hidden word.
'ERITH' is hidden within 'barrier it has'.

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I've seen this clue in The Independent.

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