1 Down is the first word in the answers to each of the three mentioned clues, and is clued directly in each of them. I apologize if the wording is confusing - I'm definitely open to suggestions on how to make it clearer!
I guess shortstop also works if you wanted to go with SHORTtechnically being "first," but it is a compound word while the others aren't. Just for fun: an alternative cluing angle for STOPSHORT