Five-sided building housing the headquarters of the US Department of Defense (8)

I believe the answer is:

pentagon

(Other definitions for pentagon that I've seen before include "A shape; Arlington HQ" , "top brass" , "Five-sided polygon" , "rectangle snipped at one corner?" , "US DoD HQ" .)

I've seen this clue in The Mirror.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.