Make a typo, say

ERR

Mistakes often happen when fingers slip on the keyboard during fast typing.

"Make a typo" hints at a mistake in writing, and "say" signals this is a simple definition. The answer is "ERR," a short word meaning to make an error—like hitting the wrong key. The clue plays on the idea of a slip-up, with "say" reinforcing that it’s a straightforward example of the word in action.