The term 'JOINS UP' can be solved by three different crossword solutions: ENLISTS, ENROLLS, and SIGNSON. ENLISTS is a verb that means to enlist or to join the military, while ENROLLS is a verb that means to register or to sign up for something. Lastly, SIGNSON is a verb that means to sign a document or agreement. All three of these words refer to the act of joining something, whether it be a military organization, a school, or a contract.