Objection over final Soviet province (6)

I believe the answer is:

oblast

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'soviet province' is the definition.
'oblast' can be an answer for 'province' (thesaurus). I am unsure of the 'soviet' bit.

'objection over final' is the wordplay.
'objection over' becomes 'ob' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'final' becomes 'last' (synonyms).
'ob'+'last'='OBLAST'

Can you help me to learn more?

(Other definitions for oblast that I've seen before include "Russian district" , "Part of Soviet Union" , "Russian division" .)

I've seen this clue in The Independent.

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