Q: What does "bullying beat" mean? There was the following line in New Yorker's (January 18) weekend book review titled, "A Startup Fairy Tale and the Dark Side of Yoga." 

"Emily Bazelon returns to the bullying beat in this week's New York
  Times Magazine, in a story about bullies, their victims, and a third
  party of Internet activists that seeks justice when authorities
  won't."

http://www.newyorker.com/online/blogs/books/2014/01/weekend-reading-a-startup-fairy-tale.html
I don't think I've met the word, "bullying beat" before. What doe's "Emily Bazelon returns to the bullying beat" mean? 
Is "the bullying beat" a common English word ?

A: Beat is used here in the sense of "the territory someone regularly observes". It was first used of watchmen and policemen, but has for a century also been applied to journalists: reporters "cover" the sports beat, the city hall beat, the theatre beat. 
So saying Ms. Bazelon "returns to the bullying beat" means that bullying is a subject she is familiar with and has often written about in the past.
