Russian leader made his mark about fifty (6)
I believe the answer is:
stalin
'russian leader' is the definition.
(I've seen this in another clue)
'his mark about fifty' is the wordplay.
'his mark' becomes 'stan' (I can't explain this - if you can you should give a lot more credence to this answer).
'about' is an insertion indicator.
'fifty' becomes 'li' (I've seen this in other clues).
'stan' enclosing 'li' is 'STALIN'.
'made' is the link.
Can you help me to learn more?
(Other definitions for stalin that I've seen before include "Communist dictator" , "Tyrant - last in (anag)" , "Former Georgian theology student, d. 1953" , "Former Soviet leader" , "Russian WW2 leader" .)