Clubs strongly supporting demand (7)

I believe the answer is:

callfor

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'clubs strongly' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'supporting demand' is the wordplay.
I cannot quite see how this works, but
'supporting' could be 'for' (being for something means supporting it) and 'for' is present in the answer.
'demand' could be 'call' (call is a kind of demand) and 'call' is located in the answer.
No letters remain.
This explanation may well be incorrect...

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I've seen this clue in The Daily Express.

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