Sat ___ (GPS, to Brits)

NAV

Think of the British term for the system that guides drivers, starting with "N."

In British English, "sat nav" is short for "satellite navigation," which is what Americans typically call GPS. The clue plays on this regional difference by dropping the "sat" part and leaving "___ nav" to hint at the answer. Since the answer is just the abbreviation for "navigation," the solution is "NAV."