I think I know what you're talking about.

For me a 'dirty' high would be feeling anxiety, paranoia, fear, etc.
A 'clean' high (for me anyway) would be a head high, aka a sativa. Body highs are nice but I don't associate with 'clean'.

Also a 'dirty' high can describe weed laced with something, especially if you don't know its laced. you then feel a different high which you're not used to, it can be unpleasant hence the term 'dirty'.