Starts to serve time in Russian prison (4)

I believe the answer is:

stir

'prison' is the definition.
(informal term for prison)

'starts to serve time in russian' is the wordplay.
'starts to' says to take the initial letters.
The first letters of 'serve time in russian' is 'STIR'.

(Other definitions for stir that I've seen before include "Cause to move in slangy prison" , "College" , "move very slightly, or agitate" , "prompt" , "Move; wake" .)

I've seen this clue in The Guardian and The Telegraph.

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