Power gained by tough approach as victor eliminates resistance (6)

I believe the answer is:

vigour

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'power' is the definition.
(I have seen 'Vital power ' mean 'vigour' so perhaps 'power' could also mean 'vigour')

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for vigour that I've seen before include "Energy, forcefulness" , "Great strength and energy" , "life" , "Stamina" , "Force" .)

I've seen this clue in The Irish Times.

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