Trees in this region have vanished we're told (7)

I believe the answer is:

argonne

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'trees in this region have vanished we're told' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

This is the entire clue.

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(Another definition for argonne that I've seen is " Forested area of First World War".)

I've seen this clue in The Independent.

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