A Highlander, perhaps, that's in Berkshire (5)
I believe the answer is:
ascot
'that's in berkshire' is the definition.
(I've seen this before)
'a highlander' is the wordplay.
'highlander' becomes 'scot' (I've seen this in another clue).
'a'+'scot'='ASCOT'
'perhaps' is the link.
(Other definitions for ascot that I've seen before include "Where ladies wear new hats" , "English horse racing venue on coast" , "Town with racecourse" , "prestigious meeting" , "English racecourse in Berkshire" .)