Soviet revolutionary (5)
I believe the answer is:
lenin
'soviet revolutionary' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lenin that I've seen before include "Soviet Union's first premier" , "Russian revolutionary" , "Marxist theoretician" , "Vladimir Ilyich Ulyanov, d. 1924" , "Leader of the Russian Revolution" .)