Journo to broadcast on cultism (9)
I believe the answer is:
columnist
'journo' is the definition.
(I know that columnist is a type of journo)
'broadcast on cultism' is the wordplay.
'broadcast' indicates anagramming the letters (letters scattered or cast around).
'on'+'cultism'='oncultism'
'oncultism' is an anagram of 'COLUMNIST'.
'to' acts as a link.
(Other definitions for columnist that I've seen before include "Contributor to newspaper" , "writer" , "Journalist making regular contributions" , "leader?" , "Waters or O'Toole, say" .)