1. Lost gas doesn't cut it (7) 2. Ginger girl swallows a fish (8) 3. Motorway with one-way sign causes squash (6) 4. Kai-laan provides arms to slay the emerald dragon (5,5)
. . . . to clarify, Mustard gas was originally assigned the name LOST, after Lommel and Steinkopf, who first proposed the military use of sulfur mustard to the German Imperial General Staff.