Announcement from Roman capitol (12)
I believe the answer is:
proclamation
'announcement' is the definition.
('proclamation' can be a synonym of 'announcement')
'from roman capitol' is the wordplay.
'from' is an anagram indicator (from the letters).
'roman'+'capitol'='romancapitol'
'romancapitol' anagrammed gives 'PROCLAMATION'.
(Other definitions for proclamation that I've seen before include "Public announcement" , "Official public declaration" , "Official announcement" .)