Am now a changed person (5)
I believe the answer is:
woman
'person' is the definition.
(woman is a kind of person)
'am now a changed' is the wordplay.
'a changed' indicates anagramming the letters.
'am'+'now'='amnow'
'amnow' with letters rearranged gives 'WOMAN'.
(Other definitions for woman that I've seen before include "person not going on stag-night" , "Mature female" , "Adult female" , "Lady" , "See 16" .)