Present, say, without a contrary belief (6)
I believe the answer is:
heresy
'contrary belief' is the definition.
(I've seen this before)
'present say without a' is the wordplay.
'present' becomes 'here' (both can mean in attendance).
'without' indicates named letters should be taken away.
'say' with 'a' taken away is 'sy'.
'here'+'sy'='HERESY'
(Other definitions for heresy that I've seen before include "Heterodoxy" , "Opinion opposed to orthodox belief" , "Religious unorthodoxy" , "Unorthodoxy - apostasy" , "Unbelief" .)