The reformed, almost agreeable native (6)
I believe the answer is:
ethnic
'native' is the definition.
(thesaurus)
'the reformed almost agreeable' is the wordplay.
'reformed' indicates anagramming the letters.
'almost' means to remove the last letter (most of the word but not all of it).
'agreeable' becomes 'nice' (I've seen this before).
'nice' with its last letter taken away is 'nic'.
'the' anagrammed gives 'eth'.
'eth'+'nic'='ETHNIC'
(Other definitions for ethnic that I've seen before include "To do with race or nationality" , "Of the distinct ways of living of a particular group of people" , "To do with race and its customs" , "Of nations and races" , "Having a common race or cultural tradition" .)