Imply ethos is wrong with this sort of belief (10)
I believe the answer is:
polytheism
'this sort of belief' is the definition.
'imply ethos is wrong' is the wordplay.
'is wrong' is an anagram indicator.
'imply'+'ethos'='implyethos'
'implyethos' with letters rearranged gives 'POLYTHEISM'.
'with' is the link.
(Other definitions for polytheism that I've seen before include "worshipping many gods" , "Worship of more than one god" , "Belief in more than one god" .)