Took horse round for cowboy event (5)
I believe the answer is:
rodeo
'cowboy event' is the definition.
(exhibition or show featuring cowboys)
'took horse round' is the wordplay.
'took horse' becomes 'rode' (rode a horse).
'round' becomes 'o' (round can mean a round object).
'rode'+'o'='RODEO'
'for' acts as a link.
(Other definitions for rodeo that I've seen before include "Cowboy riding contest" , "Wild West contest" , "Contest of cowboy skills" , "display of cowboy skill" , "American show" .)