The crossword solution for the term 'Leaking Substance' is Urea, which is a colorless, crystalline organic compound that is highly soluble in water. It is an important source of nitrogen for plants and is also found in many animals, including humans, as a metabolic by-product. Urea is produced commercially from ammonia and carbon dioxide and is used in fertilizers, animal feed, and as a raw material for the manufacture of plastics.