The term WORKED FOR M can be summarized by the crossword solution SPIED, which is a five-letter word. Spying is an activity in which someone secretly observes or investigates another person or group of people. It is often done for intelligence gathering purposes, such as gathering information about an enemy or competitor. Spying can also be done for personal reasons, such as to gain an advantage in a business or personal relationship. In this case, the person who worked for M was likely a spy, gathering information on behalf of their employer.