At least in my experience “fair use” doesn’t have a solid definition. My understanding is that you CAN use copyrighted material as long as it’s for NON COMMERCIAL USE and you don’t use the ENTIRE work.
For example using 5-10 seconds of a copyrighted music piece in a demo reel when applying for employment should not get you into legal hot water.
Using the ENTIRE song in a demo reel FOR SALE would land you in court.
Fair use also applies for the news:
The Rolling Stones were in Boston recently- local TV and radio news is able to use small segments of the concert in their reports regardless of the copyrights. If they televised or broadcast the ENTIRE concert they step into infringement.
