Naive, inexperienced (9)
I believe the answer is:
unworldly
This clue is a double definition.
'naive' is the first definition.
(similar in meaning)
'inexperienced' is the second definition.
(thesaurus)
(Other definitions for unworldly that I've seen before include "Having little awareness of the realities of life" , "Spiritual, not materialistic" , "Naive" .)