The term 'SOAP SUBSTANCE' can be broken down into two crossword solutions: LYE (3 letters) and PALMOIL (7 letters). LYE is a type of alkali, which is a highly basic substance that is used in the production of soap. Palm oil is a type of vegetable oil derived from the fruit of the oil palm tree, and it is also used in the production of soap. Both LYE and palm oil are essential ingredients in the manufacture of soap.