The crossword solution for the term SMART, FOR ONE is SPY. A SPY is a person who works in espionage, which is the practice of gathering information or intelligence about an enemy or competitor. Spies often use disguises and other tactics to remain undetected while gathering information. They may also be involved in sabotage, sabotage being the intentional disruption of an enemy's operations. Spies are typically employed by governments, military organizations, or private corporations.