Lendl of tennis (4)
I believe the answer is:
ivan
'lendl of tennis' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ivan that I've seen before include "Russian tsar called 'the Terrible'" , "Name of six Russian tzars" , "in Russian history" , "Fellow" , "Russian boy's name" .)