Harbinger, messenger (6)
I believe the answer is:
herald
I believe this clue is a double definition.
'harbinger' is the first definition.
(I know that harbinger can be written as herald)
'messenger' is the second definition.
(I know that herald is a type of messenger)
(Other definitions for herald that I've seen before include "College of Arms official" , "Bringer of news" , "Proclaim the approach of, like archaic messenger" , "Presage for old announcer" , "Proclaimer" .)