beat reporter; assigned reporter
A journalist assigned to cover a specific person, organization, or field, often to obtain exclusive or up-to-date information. Common in political and sports journalism.
The prime minister's beat reporter is stationed at the official residence every day.
He writes articles as a beat reporter for a professional baseball team.
Compound of 番 (ban, 'watch' or 'duty') and 記者 (kisha, 'reporter'). The term likely originated in journalism to describe reporters assigned to monitor a specific person or beat.