Win 4 Street Scene races, it doesn't seem to matter which ones, difficulty also doesn't seem to matter.
You'll then be shown a location on the map, first one will be for a Mustang. Win that and the achievement is yours!
Edit: Tip from WillGoss12 in the comments below; Just to add : you can pin the street races that you need and track them in your Accolades tab, thank to STEVIO2175 who made a video on YouTube about it