Court sport (6)
'court sport' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tennis that I've seen before include "Ball game with a net" , "Sent in (anag.)" , "Sent in, oddly, to play a sport" , "Sport with grand slams?" , "Evil trap set up for game" .)
(Other definitions for basketball that I've seen before include "Harlem Globetrotters' sport" , "that's contested in court" , "Team game" , "Game involving two hoops" , "American game" .)
(Other definitions for netball that I've seen before include "Team game for tall Ben" , "Game for women or girls" , "After this, you get to serve again" , "Team game/sport" , "Seven-a-side team game -- all bent (anag)" .)