The beautiful game (6)
(Other definitions for soccer that I've seen before include "... players playing this (colloquially)" , "The beautiful game?" , "Informally, game" , "Ball game" , "Roy Keane's game" .)
'the beautiful game' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for football that I've seen before include "controversial issue" , "Gambling on soccer results" , "The beautiful game, some say" , "Liverpool or Everton, for example" , "Strange ballot of the game" .)