Toast when drinking to tosspot, sir? (6)

I believe the answer is:

prosit

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

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

(Other definitions for prosit that I've seen before include "Drinking call, good health to you" , "I sport during German toast to your health" , "Drinking salutation" , "Happy days, perhaps" , "Good luck to you" .)

I've seen this clue in the Sydney Morning Herald.

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