What each Down answer needs from its clue in order to make sense

FIRSTTWOLETTERS

Think about how the first part of each Down clue might serve as a hidden instruction—look for a pattern at the very start.

This clue is a self-referential hint about how the Down answers work. Every Down answer in the puzzle is formed by taking the first two letters of its clue—for example, if a Down clue was "Apple pie ingredient," the answer would start with "AP." The answer "FIRSTTWOLETTERS" literally spells out what you need to do: grab the first two letters of each Down clue to solve it. It’s a meta-clue pointing to the puzzle’s own construction.