Original sinner (4)
I believe the answer is:
adam
'original sinner' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for adam that I've seen before include "the first orphan?" , "Man No. 1" , "Father of Cain and Abel" , "who transformed Palladian architecture?" , "First man in the Bible" .)