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Extremely good for son, Whitehaven seance has lifted hearts and discharged energy (4,1,9)

Ross

I believe the answer is:

with a vengeance

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'extremely' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

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(Another definition for with a vengeance that I've seen is " really meaning it?".)

I've seen this clue in The Telegraph.
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