Smokeless Explosive Made With Nitroglycerine
Puzzle 12 of Building a House Hard Pack
Question is: Smokeless Explosive Made With Nitroglycerine
and the answer is: CORDITE
Word Meaning:
CORDITE — A smokeless propellent made by combining two high explosives, nitrocellulose and nitroglycerine, used in some firearm ammunition.
Definitions from Wiktionary.