Tennis's "King of Clay" (5)
I believe the answer is:
nadal
'tennis's king of clay' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nadal that I've seen before include "Top tennis player" , "Star with a 30 [RACKET]" , "Rafael __, Spanish tennis player" , "court figure" , "tennis champion" .)