The crossword solution for the term 'LIGHT FILL' is 'NEON'. NEON is a chemical element with the symbol Ne and atomic number 10. It is a noble gas that is colorless, odorless, and tasteless. NEON is used in a variety of applications, including lighting, advertising, and scientific research. It is also used in the production of lasers and television tubes. NEON is one of the most abundant elements in the universe and is found in trace amounts in the Earth's atmosphere.