Left leader number 50 to get overthrown (5)
I believe the answer is:
lenin
'left leader' is the definition.
'Lenin' can be an answer for 'leader' (Lenin is an example). I am unsure of the 'left' bit.
'number 50 to get overthrown' is the wordplay.
'number' becomes 'no' (abbreviation).
'50' indicates taking half (50 percent of the letters).
'to get' says to put letters next to each other.
'overthrown' becomes 'leni' (I am not sure about this - if you are sure you should believe this answer much more).
'no' with half the letters taken is 'n'.
'n' put after 'leni' is 'LENIN'.
Can you help me to learn more?
(Other definitions for lenin that I've seen before include "Russian revolutionary" , "Leader of the Russian Revolution" , "Vladimir Ilich Ulyanov" , "First leader of USSR" , "Soviet Union's first premier" .)