Communist leader left number rising (5)
I believe the answer is:
lenin
'communist leader' is the definition.
(I've seen this before)
'left number rising' is the wordplay.
'left' becomes 'l' (common abbreviation).
'number' becomes 'nine' (nine is a number).
'rising' is a reversal indicator (letters written upwards in a down clue).
'nine' reversed gives 'enin'.
'l'+'enin'='LENIN'
(Other definitions for lenin that I've seen before include "Linen for Communist" , "Vladimir Ilyich -, Soviet premier" , "Leader of the Russian Revolution" , "Russian revolutionary" , "Vladimir Ilich Ulyanov" .)