The term LEAK FIX can be solved by the crossword solution PLUG, which is a four-letter word. A PLUG is an object that is used to fill a hole or gap in order to prevent the passage of air, water, or other substances. Plugs are commonly used to stop leaks in pipes, tanks, and other containers. They are also used to seal openings in walls, floors, and ceilings. Plugs are available in a variety of materials, including rubber, plastic, metal, and wood.