Brothels in Kidderminster pooling capital (8)

I believe the answer is:

helsinki

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'capital' is the definition.
(capital of Finland)

'brothels in kidderminster pooling' is the wordplay.
'HELSINKI' is hidden within the letters.
But, I'm uncertain how this is indicated.

Can you help me to learn more?

(Other definitions for helsinki that I've seen before include "Main city of Finland" , "Finland's largest city" , "foreign capital" , "Capital of Finland" , "Nineteen fifty two Olympics city" .)

I've seen this clue in The Independent.

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