As far as I am aware, no one has produced a spider clown yet, so no one knows for sure.

However, when people say that spider is dominant, they mean in relation to normal, specifically the normal gene on the spider locus. And when people say clown is recessive, they mean in relation to the normal gene on the clown locus. Unless spider and clown are on the same locus, those are 2 different normal genes, but even if they are on the same locus, it says nothing about the relationship between spider and clown.

It is very possible to have a snake display both a dominant and a recessive trait at the same time, because they are on different loci. Some examples: honey bee, albino spider, spied, etc.