Crossword Genius

'K' is wrestling with Pat (sumo) (9)

Ross

I believe the answer is:

potassium

'k' is the definition.
('potassium' can be a synonym of 'k')

'is wrestling with pat sumo' is the wordplay.
'wrestling with' indicates anagramming the letters.
'pat'+'sumo'='patsumo'
'is' mixed up with 'patsumo' can make 'POTASSIUM'.

(Other definitions for potassium that I've seen before include "Reactive metal element" , "Element K" , "... is its atomic number: symbol K" , "Silvery metallic element" , "Soft metal, symbol K" .)

I've seen this clue in The Guardian.
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