Clue: Litmus-reddening substance

Answer: ACID

Length: 4

---

Similar Clues:

• Substance-abusing star of "Mean Girls" in headlines (LILO with 4 letters)
• Belladonna substance (ATROPINE with 8 letters)
• La Brea pits' substance (TAR with 3 letters)
• Wood-finishing substances (SHELLACS with 8 letters)
• Gelling substance (AGAR with 4 letters)
• Blobby substance (GOO with 3 letters)
• Cellular substance, for short (RNA with 3 letters)
• Flue substance (SOOT with 4 letters)
• Paving substances (e.g. ASPHALTS with 8 letters)
• Litmus reddener (ACID with 4 letters)