Hint: The clue for 57A says that "TV SETS" is a hint. Wait a minute! There are four "TVs" appearing in symmetrically-placed grid entries.
Hint: "SET" can have several different meanings, but I'm going for the one that means "put, lay, or stand (something) in a specified place or position".
Hint: What's with all of those "ONs" at the bottom of the grid? Is the constructor trying to tell us something?
Hint: Check the letters that have been placed "on", or in other words, "set" atop the TVs?
Hint: In case you're still wondering, the Easter egg at 33A should confirm the familiar phrase for you.