In order to see the mission, you need to select a HVT that's in the area. It appears after you complete the mission. Your two options are Normal and Hard and it is located inside a parking garage.
It's not supposed to be there. From the state of the game post:
MIDTOWN WEST CLINIC
Following the maintenance this week, we saw several reports of a new mission appearing on the map. We want to clarify that this is not intended or some kind of teaser.
So if it is not a teaser of a future mission to be implemented with, say, the next DLC then WTF is it? How can it just randomly appear on the map? A previous, aborted mission then?
Tell you what, the Dev team's communication leaves much to be desired.......