Start of a joke

KNOCKKNOCK

Think of the two words you might say before delivering a playful punchline at someone’s door.

This clue plays on the classic setup for a "knock-knock joke," where the joke always begins with someone saying "Knock knock." The answer is simply the two words combined into one without a space, which is how it fits into the crossword grid. It’s a straightforward cultural reference—anyone familiar with this type of joke will recognize it instantly.