What every "O" in this grid represents

PIP

Think of the small dots on a die that might fill a circle in this puzzle.

This clue plays on the idea of "O" as a letter and its visual resemblance to something else. In crosswords, "O" can look like a small dot or circle, which is often called a "pip"—like the dots on dice or dominoes. The answer "PIP" is a clever nod to that shape, turning the letter into a tiny, round mark. It’s a simple but clever visual pun.