Answer: CLINKER

AnswerCrossword Clue
CLINKERSour note
CLINKERWrong note, in slang
CLINKEROne of Edgar Bergen's aides.
CLINKERFurnace impediment.
CLINKERBoo-boo
clinkerto make furnace slag
clinkerA brick with a vitrified surface
clinkerThe stony residue from burned coal or from a furnace