"Yipes!"

EEK

This exclamation of surprise is often heard when someone is startled by a mouse.

The clue "Yipes!" is an exclamation of surprise or fear, and "EEK" is a common onomatopoeic expression for the same reaction. Both words convey a sudden, startled response, making "EEK" a fitting answer. It’s a straightforward example where the clue and answer share the same meaning in a playful, concise way.