Sporting contest (12)
'sporting contest' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for championship that I've seen before include "Contest - advocacy" , "Sporting contest to decide overall winner" , "title" .)
(Other definitions for match that I've seen before include "tie" , "Contest; correspond" , "Lighter; contest" , "Sporting event" , "Marriage; game" .)