Announcer arrested after intervention by artist (6)
I believe the answer is:
herald
'announcer' is the definition.
(herald can mean to announce or predict)
'arrested after intervention by artist' is the wordplay.
'arrested' becomes 'held' (held in custody).
'after intervention by' means one lot of letters goes inside another (to intervene can mean to become involved in).
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'held' going around 'ra' is 'HERALD'.
(Other definitions for herald that I've seen before include "Proclaim the approach of, like old messenger" , "Usher in; proclaim" , "College of Arms official" , "Announce, presage" , "Harbinger, precursor" .)