Crossword Genius

Free-style wrestling can leave one so exhausted (3-2)

Ross

I believe the answer is:

all-in

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'exhausted' is the definition.
('all in' can mean exhausted)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for all-in that I've seen before include "Pooped" , "Exhausted - comprehensive" .)

I've seen this clue in The Globe and Mail.
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