Traffic Jam

Traffic Jam is a miscellaneous quest in Fallout 4.

Detailed walkthrough
Ask Deb at Bunker Hill for a job. She'll inform that some nearby feral ghouls pose a threat to Bunker Hill and that they need to be removed. Go to the National Guard training yard and kill the feral ghouls, and then return to Deb to collect your reward.

If the area had already been cleared previously then the Sole Survivor can directly ask for the reward in the same conversation.