Unworldly, green (5)
I believe the answer is:
naive
I believe this clue is a double definition.
'unworldly' is the first definition.
(similar in meaning)
'green' is the second definition.
(green can mean naive or innocent)
(Other definitions for naive that I've seen before include "Ingenous, easy to gull" , "Lacking judgment" , "Unsophisticated and gullible" , "Natural, unaffected" , "Unaffected or guileless" .)