When you search for Broadcast clips on Muck Rack, each clip will list audience metrics beneath the clip's air date.
Audience metrics are provided by Nielsen, and denote the viewership or listenership in the market where the broadcast clip aired.
National Audience
The total viewership or listenership of the clip from those across the nation.
Local Audience
The total viewership or listenership of the clip from those in the local area.