Hooter goes at end of great championship game (5,4)
I believe the answer is:
super bowl
'championship game' is the definition.
(championship game in American football)
'hooter goes at end of great' is the wordplay.
'hooter' becomes 'owl' (owls hoot).
'goes at end of' means one lot of letters go next to another.
'great' becomes 'superb' (I've seen this in another clue).
'owl' put after 'superb' is 'SUPER BOWL'.
(Other definitions for super bowl that I've seen before include "US football final" , "sporting occasion" , "Championship game of the US NFL" , "NFL championship match" , "American sporting event" .)