Each across clue also describes how similar the across entry is to the five-letter meta answer. =that letter is not in the answer. =that letter is in the answer, but in a different place. =that letter is in the answer in the same place.
Fun fact: the 1A of the 3 Crosswordles I've made so far are my usual first 3 guesses in any of the multi-word Wordle spinoffs like Dordle, Quordle, and Octordle. On regular Wordle I play on hard mode so I have to adjust from my guesses if any of the letters match.
This puzzle's title comes from the fact that the 3 matching letters are STD, yikes (not planned ahead of time). But the title does also fit with the meta answer.