Arthur's Seat visited by large number (7)
I believe the answer is:
camelot
'arthur's seat' is the definition.
(court of King Arthur)
'visited by large number' is the wordplay.
'visited by' becomes 'came' (I am not sure about this - if you are sure you should believe this answer much more).
'large number' becomes 'lot' (a large amount).
'came'+'lot'='CAMELOT'
Can you help me to learn more?
(Other definitions for camelot that I've seen before include "Mythical court" , "Mythical British kingdom" , "King Arthur court - or JFK's" , "Musical about King Arthur" , "Location of King Arthur's court" .)