Mouse almost thrashed huge wrestler (4)

I believe the answer is:

sumo

I'm a little stuck... Click here to teach me more about this clue!

'huge wrestler' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for sumo that I've seen before include "slappers fighting?" , "Grappling" , "Kind of wrestling" , "one of the martial arts" , "Japanese wrestling with big fat men" .)

I've seen this clue in The Sun.

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