Russia's plain-spoken measure (6)

I believe the answer is:

steppe

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'russia's plain' is the definition.
'steppe' can be an answer for 'plain' (steppe is a kind of plain). I'm unsure of the 'russia's' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for steppe that I've seen before include "(Russian) grassy plain" , "Large treeless area of Siberia" , "plain territory" , "Dry grassy plain of eastern Europe and Asia" , "crosses Siberia" .)

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

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