Green’s Dictionary of Slang

run-out powder n.

[a fig. SE powder that inspires speed; note powder v.1 ]

In phrases

give (someone) a run-out powder (v.) (also ...a walk-out powder)

[1910s] (US) to dismiss, to send packing.

take a run-out powder (v.) (also take a run-out)

[20C+] to escape, to run away.