My story of a guy with poor habit being reformed (13)
I believe the answer is:
autobiography
'my story' is the definition.
(someone's life story)
'a guy with poor habit being reformed' is the wordplay.
'with' means one lot of letters go next to another.
'being reformed' indicates anagramming the letters.
'poor'+'habit'='poorhabit'
'guy' after 'poorhabit' is 'poorhabitguy'.
'poorhabitguy' is an anagram of 'utobiography'.
'a'+'utobiography'='AUTOBIOGRAPHY'
'of' is the link.
(Other definitions for autobiography that I've seen before include "Person's life story written by the subject" , "A person's account of their life" , "Personal account of one's life" , "Story of one's life" , "Literary genre" .)