Tennis star Lendl (4)
I believe the answer is:
ivan
'tennis star lendl' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ivan that I've seen before include "First tsar of Russia" , "Name of six Russian tzars" , "Russian ruler - a Terrible one" , "Tsar - 197> the Terrible" , "his progress in history was terrible!" .)