The term 'close watch' can be broken down into four crossword solutions: TABS (4 letters), VIGIL (5 letters), EYE (3 letters), and GUARD (5 letters). TABS is an acronym for 'tactical air navigation system, ' which is a system used by the military to track aircraft. VIGIL is a noun meaning 'a period of keeping awake during the time usually spent asleep, especially to keep watch or pray.' EYE is a noun meaning 'the organ of sight, ' and GUARD is a verb meaning 'to watch over or protect.' Finally, EAGLEEYE is an adjective meaning 'having very keen vision.' All of these words together describe the concept of keeping a close watch, whether it be through a navigation system, staying awake, using one's eyes, protecting something, or having sharp vision.