With 60-Across, pop rock band behind "Radioactive" ... or what you might do after discovering this puzzle's theme (7)

I believe the answer is:

imagine

(Other definitions for imagine that I've seen before include "John Lennon classic (just think of it!)" , "Picture in one's mind" , "Believe to be so, suppose" , "Classic Lennon song" , "Devise" .)

I've seen this clue in the Universal.

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.