The term 'Chimney Lining' refers to the process of installing a lining in a chimney to protect it from the heat and corrosive byproducts of burning fuel. The lining also helps to reduce the risk of fire and smoke damage. The crossword solution for this term is 'SOOT', which is a black, powdery substance that is produced when fuel is burned. SOOT is one of the main components of chimney lining and is used to help insulate the chimney and protect it from the heat of the fire.