Rear champion players (8)
I believe the answer is:
backside
'rear' is the definition.
('backside' can be a synonym of 'rear')
'champion players' is the wordplay.
'champion' becomes 'back' (I've seen this in other clues).
'players' becomes 'side' (I've seen this before).
'back'+'side'='BACKSIDE'
(Other definitions for backside that I've seen before include "Behind" , "Bottom" , "Seat" , "Buttocks" , "Rear" .)