Clear gesso is a new one for me too. As gesso, by definition, has filler in it, clear gesso is kind of a misnomer. I'm guessing it's a thick glaze. When I have it on hand I sometimes use a theatrical paint product called Rosco CrystalGel
. It's about the thickness of peanut butter. You can apply it with a palette knife for texture or just use it as a sealant. Because it's styrene-based rather than vinyl-based like white glue or most acrylics, it's not rubbery when dry and you can sand it. I wonder if clear gesso might be the same thing packaged for a different market. That being said, I've never found an acrylic gesso that I like. They're all essentially just white acrylic paint and are too rubbery to sand smooth.
Zoma, I love your partner-matching chart. Drawing one should be one of the requirements for swap co-ordinators!