Patron's legal right to appear in court (6)
I believe the answer is:
client
'patron's' is the definition.
(thesaurus)
'legal right to appear in court' is the wordplay.
'legal right' becomes 'lien' (I've seen this before).
'to appear in' indicates putting letters inside.
'court' becomes 'ct'.
'lien' going into 'ct' is 'CLIENT'.
(Other definitions for client that I've seen before include "Buyer" , "Professional person's customer" , "Professional's customer" , "One represented by lawyer" , "person lawyer represents" .)