Spontaneous individual assured of success (7)
I believe the answer is:
natural
This might be a double definition.
'spontaneous' is the first definition.
(synonyms)
'individual assured of success' is the second definition.
'natural' can be an answer for 'success' (natural is a kind of success). I'm not certain of the 'individual assured of' bit.
Can you help me to learn more?
(Other definitions for natural that I've seen before include "Not artificial or man-made" , "Relaxed, unaffected" , "Normal; not sharp or flat" , "Unaffected - native" , "Not artificial; off-white" .)