"Hey!"

PSST

This quiet sound is often used to get someone’s attention without speaking loudly—think of a sneaky whisper in a crowded room.

The clue uses a bit of misdirection by giving a loud greeting ("Hey!") to hint at its opposite—a quiet, hushed sound. "Psst" is the noise you make to get someone's attention without speaking aloud, playing on the contrast between the clue’s bold tone and the answer’s sneaky whisper. It’s a classic crossword trick where the surface meaning points away from the actual answer. Think of it like a wink to solvers who catch the reversal.