Related Clues:
- Discreet summons
- Attention-getting whisper
- Sound for attention
- "Yo!" in the library
- Start of an explanation, perhaps
- Tap-on-the-shoulder alternative
- It ain't exactly "Hey!"
- Sound from a test cheater, say
- Confidential warning
- 'Don't tell anyone, but...'
- Hushed ''Hey!''
- Classroom nudge
- Sibilant call
- Subtle signal
- Verbal elbow?