Severe blow being kettled in extremist rally (7)

I believe the answer is:

mistral

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'severe blow being kettled' is the definition.
I can't tell whether this defines the answer.

'in extremist rally' is the wordplay.
'in' indicates the answer is hidden within the clue.
'MISTRAL' is hidden in the letters of 'extremist rally'.

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(Other definitions for mistral that I've seen before include "Strong wind down the 20 valley" , "Violent northeast wind of southern France" , "Strong north wind of southern France" , "A harsh blow" , "That's a blow" .)

I've seen this clue in The Independent.

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