The crossword solution for the term 'Tough to Clean' is 'STAINED'. STAINED items are difficult to clean because the stain has penetrated the material, making it hard to remove. Depending on the type of stain, different cleaning methods may be required to remove it. For example, some stains may require special detergents or solvents, while others may need to be treated with a specific cleaning product. In some cases, professional cleaning services may be needed to remove tough stains.