Related Clues:

• Users drop it
• The 'A' in DNA
• Aid to digestion
• Glandular output
• Spitefulness
• Source of DNA evidence, often
• Heartburn cause
• Base antagonist?
• Beyond sarcastic
• See 43 Across
• Part of RNA
• Sulphuric or nitric
• Boric, e.g.
• Low-pH substance
• Sour-tasting substance