Note one certain to be a success (7)
I believe the answer is:
natural
'success' is the definition.
(I know that natural is a type of success)
'note one certain to be a' is the wordplay.
I cannot really understand how this works, but
'note' could be 'n' (abbreviation) and 'n' is located in the answer.
'one' could be 'a' (a thing is one thing) and 'a' is present in the answer.
'a' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for natural that I've seen before include "Plain - lifelike" , "Unsophisticated" , "Not disguised" , "Innate, inborn" , "character on the staff" .)