The term 'Drug Source' can be broken down into two crossword solutions: 'HEMP' (4 letters) and 'Apothecary Shop' (15 letters). HEMP is a variety of the Cannabis sativa plant, which has been used for centuries for its medicinal and industrial properties. Apothecary shops are retail stores that specialize in selling medicines and other health-related products. They have been around since the Middle Ages and were the primary source of drugs before the advent of modern pharmacies.