The term 'London's 'BIG' Bell' is referring to the famous bell known as BIG BEN. BIG BEN is the nickname for the Great Bell of the clock at the north end of the Palace of Westminster in London, England. It is the largest four-faced chiming clock and the third-tallest free-standing clock tower in the world. The crossword solution for this term is BEN, which is the shortened form of the bell's full name, Benjamin Hall.