Where horses may be game (9)
I believe the answer is:
badminton
I believe this is a double definition.
'where horses may be' is the first definition.
(ref to Badminton Horse Trials)
'game' is the second definition.
(badminton is a kind of game)
(Other definitions for badminton that I've seen before include "Game using shuttlecock" , "One sport" , "Racket sport" , "Racquet sport" , "Court game" .)