Clearing turns Silver halide into Silver-hypo complexes but these are still in the film and still may brown or darken. Fixing is the removal of these from the film by outward diffusion into the fix solution. However, these terms are very loose. They are imprecise and there is no clear description in human language other than a series of chemical equations. Up to 5 or 6 types of complexes are forming in Sodium Thiosulfate and more form in Ammonium Thiosulfate. These complexes are "clear" compared to the Silver halides which are milky or cloudy.