Cheers poison-swallowing sovereign (7)

I believe the answer is:

tsarina

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'sovereign' is the definition.
(I know that tsarina is a type of emperor)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for tsarina that I've seen before include "companion of emperor" , "Nicholas's wife" , "Catherine, say" , "queen" , "Wife of an old Russian emperor" .)

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

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