Flare up?

NOVA

Think of a sudden, brilliant burst of light in space that briefly outshines entire stars—this cosmic event shares its name with a Latin word meaning "new."

"Flare up?" hints at a sudden burst of light or energy, which fits "nova"—a star that briefly becomes extremely bright. The question mark signals wordplay, suggesting the answer isn’t literal (like a temper flare-up) but astronomical. It’s a classic crossword trick where a common phrase takes on a scientific meaning.