In painting/finishing...what constitutes a "clear"

I've had a Purdy 100% White Natural Bristle brush for years. Don't remember why I got it or when. Says it's for: Oil Based Paints, Stains and Clears. Finishing is not my strong point, what constitutes a "Clear"? I have some Epifanes High Gloss and Matte finish I want to put on a door. Those are "Clears", aren't they? I'd like to use the brush. I bought it, might as well use it and Purdy makes good stuff. Thanks for any help in clarifying my knowledge base weakness in this area. Don M

I've generally used natural bristle brushes for oil based paints and synthetic bristle for water based. I believe Epifanes is oil base so a natural bristle would be a good choice.

Based on the context of the statement, "clears" would refer to clear oil based finishes...varnishes.