The crossword solution for the term STRAW SOURCE is OAT, which stands for oats. Oats are a type of cereal grain that is widely cultivated for its edible seeds. It is a popular breakfast food and is also used in baking and other culinary applications. Oats are a good source of dietary fiber, vitamins, minerals, and antioxidants. They are also a sustainable source of straw, which is used for animal bedding, mulch, and other agricultural purposes.