First Soviet leader (5)
I believe the answer is:
lenin
'first soviet leader' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lenin that I've seen before include "Leader of the Russian Revolution" , "Marxist theoretician" , "Vladimir Ilich Ulyanov" , "Early Soviet leader" , "First premier of the Soviet Union, d. 1924" .)