Fifty nine rejected famous leader (5)
I believe the answer is:
lenin
'famous leader' is the definition.
'Lenin' can be an answer for 'leader' (Lenin is an example). I'm not sure about the 'famous' bit.
'fifty nine rejected' is the wordplay.
'fifty' becomes 'l' (roman numeral).
'rejected' shows that the letters should be reversed in order.
'nine' written backwards gives 'enin'.
'l'+'enin'='LENIN'
Can you help me to learn more?
(Other definitions for lenin that I've seen before include "First leader of USSR" , "Revolutionary leader" , "Russian revolutionary" , "Leader of the Russian Revolution" , "Revolutionary man" .)