Naive girl, genuine, mistreated (7)
I believe the answer is:
ingenue
'naive girl' is the definition.
(I've seen this before)
'genuine mistreated' is the wordplay.
'mistreated' indicates anagramming the letters.
'genuine' is an anagram of 'INGENUE'.
(Other definitions for ingenue that I've seen before include "Genuine (anag.)" , "young woman lacking experience" , "Unsophisticated girl" , "She's artless" , "Unworldly young woman" .)