... the oddball's backward, somewhat naive demeanour (7)
I believe the answer is:
deviant
'the oddball's' is the definition.
(thesaurus)
'backward somewhat naive demeanour' is the wordplay.
'DEVIANT' is hidden backwards within the letters.
However, I'm uncertain how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for deviant that I've seen before include "Nonconformist" , "(One) behaving differently from accepted standards" , "Irregular" , "Diverging from the norm or from truth" , "Twisted" .)