Court order restricting American patronage (6)
I believe the answer is:
custom
'patronage' is the definition.
(I know that custom is a type of patronage)
'court order restricting american' is the wordplay.
'court' becomes 'ct' (abbreviation used in road names).
'order' becomes 'om' (Order of Merit).
'restricting' is an insertion indicator.
'american' becomes 'us' (abbreviation for United States).
'ct'+'om'='ctom'
'ctom' enclosing 'us' is 'CUSTOM'.
(Other definitions for custom that I've seen before include "Convention" , "Regular process" , "Habitual use" , "Tradition; habit" , "Usual practice" .)