Related Clues:

• School basics, initially
• Growl
• Guttural utterance
• React like a threatened dog
• Elementary school trio
• Grammar school basics, for short
• "Don't mess with me!"
• Kennel warning
• Warning to the postman
• ''I'm mad!''
• Lab's warning
• Chow line?
• Basic education, facetiously
• 'Hands off that bone …'
• Angry warning