somebody who writes lyrics secretly for another person and they get payed to do it

A person or people that purposefully causes chaos or mischief within a group for the sake of entertainment.

When a rapper has someone write their lyrics for them, but they take the credit and record them.

One who writes the lyrics to a rap song and then someone else performs them. Often it is the better of the two rappers writing the song but not wanting the fame.

The literary equivalent of the fat old guys who sang on the Milli Vanilli records. In other words, a writer who writes under someone else's name with their consent. The so-called author gets his or her name printed on the cover and receives credit for the writing while the ghostwriter does the actual work.

Celebrity and politician autobiographies are usually ghostwritten, due to the "author" having no writing talent whatsoever. What, you think Jenna Jameson and Hillary Clinton actually wrote their books?

Ghostwriters are also disturbingly common in fiction, not that anyone gives a rat's ass that Tom Clancy doesn't actually write his crappy novels.

A 90's TV show that set the current meaning for "ghost writer" (person who write lyrics to songs but remains anonymous). It was based on a ghost who would "pick up" letters from places such as keyboards or street signs and re-arrange them to communicate with a bunch of teenagers to help them with their daily lives.