The term 'Broadway Ethel' is a reference to the iconic American actress and singer Ethel Merman. Merman was best known for her roles in Broadway musicals such as 'Annie Get Your Gun' and 'GYPSY'. She was also known for her powerful singing voice, which earned her the nickname 'The Merm'. The crossword solution for this term is 'Merman', which is a six-letter word that refers to Ethel Merman's stage name.