Can fair use be applied to an actors reel?

Answer 1

Probably, although you may wish to speak with an actual lawyer before proceeding. That being said, let's consider a demo reel in light of the "four factors."

1. "purpose and character of the use" your use isn't strictly for-profit, but it isn't strictly non-profit and educational, either. Let's call that a draw.
2. "nature of the copyrighted work" an artistic work is not going to fare well in this category. So one point against.
3. "amount and substantiality of the portion" this, along with #1, is what the courts like to look at these days. The reason they add "substantiality" along with "amount" is, if the 30 seconds you take are the iconic 30 seconds of the work, your excerpt might be considered substantial even if it's small. But if you limit your excerpts to the smallest amount possible to make the point (I was in this, I can cry on demand, I have athletic skills, I can play the guitar, whatever) you should be fine. So we'll call that one point for.
4. "effect on use upon the potential market" this used to be the big thing for the courts, but not so much lately. Still, a demo reel with you doing one monologue out of a 2-hour play is not going to significantly interrupt the revenue stream of the playwright. Another point for.

Now, aside from these, there's also the notion of "transformation" mentioned in the law, and that's what the courts have really been pushing lately. Personally, I think your use is transformative: you're taking something meant for entertainment, and you're transforming it into a means to show your suitability for a job--it's arguably equivalent to a resume. Here is where I point out that I'm not a lawyer.

I feel the need to tack on that if you're using anything in its entirety--a whole commercial, a headshot, etc--you will need permission, and if you set anything to music, you will need permission for that. But tacking together a couple seconds here and a couple seconds there (de minimis use, if you want to get fancy) shouldn't hurt anyone.