Power gained by tough approach as victor eliminates resistance (6)
I believe the answer is:
vigour
'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" .)