The term SOAP-MAKING SUPPLY is related to the process of making soap, and the crossword solution for this term is LYE, which is a three-letter word. LYE is an alkaline solution that is used in the process of making soap, and it is usually made from either sodium hydroxide or potassium hydroxide. It is a key ingredient in soap-making, as it helps to break down the fats and oils used in the process.