Large advert (6)

I believe the answer is:

poster

(Other definitions for poster that I've seen before include "'Notice, placard (6)'" , "Large sheet of paper advertising something" , "Large advertisement" , "Town near Glasgow" , "Bill or placard" .)

I've seen this clue in The Telegraph and The Times.

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.