At least three Queen’s companions in Siberian city (5)

I believe the answer is:

tomsk

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

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for tomsk that I've seen before include "Industrial city of southern Siberia - one of the Wombles" , "Siberian city; one of the Wombles" , "Russian town" .)

I've seen this clue in The Times.

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