One may be drop-down

MENU

Think of what you click to see options like "File," "Edit," or "View" at the top of a computer screen.

The clue plays on the double meaning of "drop-down." In computing, a "drop-down menu" is a list that appears when clicked, like in a toolbar or settings panel. The word "one" hints at a single example of something that fits this description, and "menu" is the most common term for it. The phrasing is simple but clever, using everyday language to point toward a tech-related answer.