Regions where the weather favours a number of trees? (6)

I believe the answer is:

climes

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'regions where the weather favours a' is the definition.
I can't tell whether this definition defines the answer.

'number of trees?' is the wordplay.
'number of' becomes 'c' (I can't explain this - if you can you should believe this answer much more).
'trees?' becomes 'limes' (lime is a kind of tree).
'c'+'limes'='CLIMES'

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I've seen this clue in the Evening Standard.

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