Group of nations misrepresent France, showing lack of faith (8)
I believe the answer is:
'lack of faith' is the definition.
(I've seen this before)
'group of nations misrepresent france' is the wordplay.
'group of nations' becomes 'un' (abbreviation for United Nations).
'misrepresent' becomes 'belie' (synonyms).
'france' becomes 'f'.
'showing' acts as a link.
(Other definitions for unbelief that I've seen before include "Lack of religious faith" , "Pagan's attitude" , "scepticism" .)