Popular opening subject of my autobiography, touching story (9)
I believe the answer is:
invention
'story' is the definition.
(thesaurus)
'popular opening subject of my autobiography touching' is the wordplay.
'popular' becomes 'in'.
'opening' becomes 'vent' (vent is a kind of opening**).
'subject of my autobiography' becomes 'i' (ie the person writing or speaking).
'touching' becomes 'on'.
'in'+'vent'+'i'+'on'='INVENTION'
(Other definitions for invention that I've seen before include "Creation of a device or new process" , "of necessity, a child?" , "untruth" , "Creation of something new" , "Offspring of necessity" .)