Authenticity is dividing field of study (7)
I believe the answer is:
realism
'authenticity' is the definition.
(thesaurus)
'is dividing field of study' is the wordplay.
'dividing' is an insertion indicator (inserted letters divide the word).
'field of study' becomes 'realm' (I've seen this before).
'is' put inside 'realm' is 'REALISM'.
(Other definitions for realism that I've seen before include "Pragmatism" , "Awareness of the facts of life" , "Acceptance of life as it is" , "Practicality of a smiler" , "Reliance on facts" .)