Crossword Genius

Stunning sort of tournament? (8)

Ross

I believe the answer is:

knockout

'stunning' is the definition.
(thesaurus)

I cannot understand how the remainder of the clue works.

(Other definitions for knockout that I've seen before include "Decisive blow" , "reverse of OK?" , "Excellent!" , "The quietus in boxing" , "Result of last punch" .)

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