Journalist rioted unexpectedly (6)
I believe the answer is:
editor
'journalist' is the definition.
(senior journalist)
'rioted unexpectedly' is the wordplay.
'unexpectedly' indicates anagramming the letters.
'rioted' with letters rearranged gives 'EDITOR'.
(Other definitions for editor that I've seen before include "Person in charge of newspaper" , "Person responsible for publication;" , "Redactor" , "One prepares a work for publication" , "Redo it and become head of publication" .)