Distraction is a feature in the Battlefield Hardline singleplayer campaign. It causes Nick to throw an empty shell casing, which will attract the attention of enemy NPCs to the location that the shell lands.
Using the Distraction is useful, and at times necessary, if the player is attempting to complete a singleplayer episode stealthily, allowing the player to alter patrol patterns and clear routes for a short time. It can also be useful for getting a criminal with a Warrant away from others in order to arrest him silently.
Distraction may be a feature in the campaign for Battlefield 1, as players can set a keybind for this ability in the Options menu.