Supreme leader – D-day operation (8)

I believe the answer is:

overlord

(Other definitions for overlord that I've seen before include "top man!" , "Feudal ruler" , "Supreme master; D-Day operation" , "WWII Operation" , "Ruler, D-day Operation" .)

I've seen this clue in The Guardian.

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.