I don't believe this tea's brewed (7)
I believe the answer is:
atheist
'i don't believe' is the definition.
(I've seen this before)
'this tea's brewed' is the wordplay.
'brewed' indicates an anagram.
'this'+'tea'='thistea'
'thistea' with letters rearranged gives 'ATHEIST'.
(Other definitions for atheist that I've seen before include "One who does not believe in the existence of a god" , "Disbeliever in gods" , "Person who does not believe in existence of a god" , "One denying existence of a god" , "One not believing in gods" .)