Unrefined person sure to succeed (7)
I believe the answer is:
natural
I believe this clue is a double definition.
'unrefined' is the first definition.
(I've seen this before)
'person sure to succeed' is the second definition.
(someone with a natural talent)
(Other definitions for natural that I've seen before include "Innate, inborn" , "Not artificial or affected" , "lacking sophistication" , "Instinctive - not surprising" , "Unsophisticated" .)