Court entertainer (6)
(Another definition for tennis player that I've seen is " racketeer revealed?".)
'court entertainer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for jester that I've seen before include "Court humorist" , "Professional clown of the middle ages" , "Funny man, once at court" , "Professional joker" , "Court entertainer (with bells on?)" .)