States 'authentic' writing (6)
I believe the answer is:
realms
'states' is the definition.
(realm is a kind of state)
'authentic writing' is the wordplay.
'authentic' becomes 'real' (I've seen this before).
'writing' becomes 'ms' (abbreviation for manuscript).
'real'+'ms'='REALMS'
(Other definitions for realms that I've seen before include "Kingdoms, domains" , "Kingdoms, or fields of activity" , "Domains ruled by king or queen" , "areas of interest" , "Kingdoms, or fields of interest" .)