One believes there are no gods (7)
I believe the answer is:
atheist
'one believes there are no gods' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for atheist that I've seen before include "One not believing in gods" , "Unbeliever" , "One denies the existence of gods" , "Person who does not believe in existence of a god" , "One who disbelieves the existence of gods" .)