The term 'BASIC SOLUTION' can be broken down into four crossword solutions: LYE (3 letters), ALKALI (6 letters), BRINE (5 letters), and TONER (5 letters). LYE is a type of alkaline solution, usually made from sodium hydroxide or potassium hydroxide, that is used for cleaning and in soap-making. ALKALI is a type of chemical compound that is basic in nature and has a pH greater than 7. BRINE is a salty solution made from water and salt, often used to preserve food. TONER is a liquid or powder solution used in printing and photocopying to transfer an image onto paper.