A Caledonian royal (5)
I believe the answer is:
ascot
'royal' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'a caledonian' is the wordplay.
'caledonian' becomes 'scot' (I've seen this in another clue).
'a'+'scot'='ASCOT'
Can you help me to learn more?
(Other definitions for ascot that I've seen before include "racing centre" , "sporting venue" , "Racecourse with royal associations" , "Berkshire town, famous for horse racing" , "Berkshire race course" .)