Clear is useless. Give it to me. I'll take it off your hands for you.
Like one of the several things Frog said, It's good for some subtle effects. It gives and indication of (something) on black shirts, brown shirts, (tone on tone) ghosting of sorts if used all by itself. You can add to that by adding in a % of any pigment...and reverse that on white tees.
Print it straight on white tees, it gives a clear snot sheet to prints..like wet water.
Some people use it to add to thick inks that are generally used for spot color, low mesh...and then use clear base to thin/exntend down those inks for sim process on high mesh for example. Don't use too much. We always used 5-10% in some cases, 15%. 20% starts to break down the integrity of the ink too much. I wouldn't do that to all inks. Not on Rutland or Unions inks that are already designed for sim process on high mesh.
Thanks
Dan