A news story stand up basically means that the journalist is physically present at the news site and communicating the story to the audience. It adds authenticity and a live feel to the news coverage.
A news story stand up usually refers to a journalist presenting a report or update directly from the scene of an event.
Well, a news story stand up is when a reporter appears on camera at the location of the news to give the latest information. It helps make the news more immediate and gives viewers a sense of being right there at the event.