Version of Tosca somewhere in Berkshire (5)
I believe the answer is:
ascot
'somewhere in berkshire' is the definition.
(town in Berkshire)
'version of tosca' is the wordplay.
'version of' indicates anagramming the letters.
'tosca' is an anagram of 'ASCOT'.
(Other definitions for ascot that I've seen before include "sporting event" , "Tosca (anag) - racecourse" , "Royal race course" , "Racecourse, home to the Gold Cup since 1807" , "course without any fences!" .)