* Clean: Free from dirt, marks, or stains.
* Disinfect: To clean something with a substance that kills bacteria or viruses.
* Scour: To clean or brighten the surface of something by rubbing it hard, typically with an abrasive or detergent.
* Scrub: To clean (something) by rubbing it hard, typically with a brush and water or detergent.
* Debase: To reduce (something) in quality or value; degrade.
Considering the meanings, none of those words are direct opposites of "clean." However:
* Debase is the word that means reducing the quality or value, so that would be considered a better antonym than the other options, as they mostly relate to cleaning something thoroughly or killing germs.
Therefore, the answer is debase.