Colorless Flammable Liquid Used as Motor Fuel
Puzzle 1 of Jane Austen Hard Pack
Question is: Colorless Flammable Liquid Used as Motor Fuel
and the answer is: BENZENE
Word Meaning:
BENZENE — (organic chemistry) An aromatic hydrocarbon of formula C₆H₆ whose structure consists of a ring of alternate single and double bonds.
Definitions from Wiktionary.