An underground group is a collective of individuals who operate in secrecy and often have a common goal. This term can be broken down into several crossword solutions, such as 'SECRET' (6 letters), 'CLANDESTINE' (11 letters), 'CATACOMB' (8 letters), 'bulbs' (5 letters), 'miners' (6 letters), and 'resisters' (9 letters). SECRET and CLANDESTINE both refer to the covert nature of the group, while catacombs and bulbs suggest a hidden or subterranean location. Miners and resisters indicate that the group may be engaged in some form of labor or resistance.