The term 'LONDONER's TUBE' is a nickname for the London Underground, which is the rapid transit system that serves Greater London and the home counties of Buckinghamshire, Essex, and Hertfordshire in the United Kingdom. The nickname is derived from the fact that the system is made up of 11 lines that are represented by different colors on the map. The crossword solution for this term is 'TELLY', which is short for television. This is because the London Underground is often referred to as the 'TUBE' due to its resemblance to a television set.