Related Clues:

• Oft-filtered fare
• Censored material
• Pornographic material
• Soot, dirt, grit
• X-rated literature
• Obscene word(s)
• Unlikely book club recommendation
• Soot; obscenities
• Tiny bit of black and blue material
• Sooty deposit
• Filth from backfiring food processors?
• Turning stomachs seeing filth
• Coarseness makes stomachs turn
• Religious teaching given to English blues singer making rude jokes
• Rio isn't involved in tourism and is in the Blue Books?