Joke, and a hint to what's literally inside 17-, 30-, 48-, and 64-Across 3 letters

Crossword clues for Joke, and a hint to what's literally inside 17-, 30-, 48-, and 64-Across 3 letters

Answer	Clue
GAG	Joke, and a hint to what's literally inside 17-, 30-, 48-, and 64-Across