Crude soul, terribly naive (9)
I believe the answer is:
credulous
'naive' is the definition.
(associated in meaning)
'crude soul terribly' is the wordplay.
'terribly' indicates anagramming the letters.
'crude'+'soul'='crudesoul'
'crudesoul' anagrammed gives 'CREDULOUS'.
(Other definitions for credulous that I've seen before include "Easily fooled" , "Too ready to believe things" , "Apt to believe without sufficient evidence" , "Gullible" , "Likely to believe" .)