What is the ruling on clothing if one has a wet dream and takes pleasure in the emission of fluid, but it later becomes clear that it is madhiy (pre-ejaculate) or a clear fluid similar to madhiy?

If you do not find the known semen with its characteristics after a wet dream, then ghusl is not obligatory upon you. As for madhy (pre-seminal fluid), wudu' is obligatory for it, and purification of whatever it has touched on the body and clothes.