Ban not everyone – only some – rejected (4)
I believe the answer is:
veto
'ban' is the definition.
(veto can mean a ban or prohibition on something)
'not everyone only some rejected' is the wordplay.
'only some' says the answer is hidden in the clue.
'rejected' says the letters should be written backwards.
'otev' can be found hidden inside 'not everyone'.
'otev' in reverse letter order is 'VETO'.
(Other definitions for veto that I've seen before include "black ball" , "Right to reject a proposal" , "The right to forbid an action" , "An overriding negative vote" , "Refuse to endorse" .)