Founder of Bolshevism (5)
I believe the answer is:
lenin
'founder of bolshevism' 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 "First premier of the Soviet Union, d. 1924" , "V. I. -, Soviet politician and revolutionary" , "Early Soviet leader" , "Revolutionary man" , "Marxist theoretician" .)