Royal racecourse (5)
I believe the answer is:
ascot
'royal racecourse' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ascot that I've seen before include "Racecourse with royal associations" , "racing centre" , "Tosca (anag) - racecourse" , "course without any fences!" , "Berkshire racecourse - coast (anag)" .)