In the online multiplayer there's a game mode called Classic Conflict. It should be the last one listed and you'll need to rank up a bit to be able to play it. Edit a loadout and make sure one of your classes has Jaws as the character. Now get into a Classic Conflict game. Once in, select your Jaws loadout. You'll now need to be shot in the head. Find an object and crouch behind it so that only your head is showing. You may want to fire a bit to attract attention. Hopefully someone will see and shoot you. As long as you don't get killed in a single shot the achievement will pop.
Of course if you don't want to do any of that, you could just play normally as Jaws. You'll likely get the achievement in a game or two.