Long __; back in the day

I believe the answer is:

ago

(Other definitions for ago that I've seen before include "In past times" , "Time past" , "Gone, past, since" , "(Years) before the present time" , "Earlier, gone by" .)

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.