Established state's Romance language (9)
I believe the answer is:
provencal
'romance language' is the definition.
(Provencal is an example)
'established state's' is the wordplay.
'established' becomes 'proven' (similar in meaning).
'state' becomes 'cal' (short for California).
'proven'+'cal'='PROVENCAL'
(Other definitions for provencal that I've seen before include "of southern France" , "Language in France" , "dialect" , "French region" , "Of the region in south-eastern France" .)