Principal location not started by court designer (9)
I believe the answer is:
architect
'designer' is the definition.
(I know that designer can be written as architect)
'principal location not started by court' is the wordplay.
'principal' becomes 'arch' (as in arch-enemy).
'location' becomes 'site' (site is a kind of location).
'not started' means to remove the first letter.
'by' is a charade indicator (letters next to each other).
'court' becomes 'ct' (abbreviation used in road names).
'site' with its initial letter removed is 'ite'.
'arch'+'ite'+'ct'='ARCHITECT'
(Other definitions for architect that I've seen before include "professional" , "Author" , "Building designer" , "Perhaps Scott" , "Wren perhaps" .)