In this mission, Damon is found in Old Bullworth Vale, and has a lot of Preppy-sounding dialogue. He asks Jimmy to beat up some Greasers by a basketball court. After Jimmy beats those Greasers up, Damon claims that they "didn't get the message" and sends Jimmy to New Coventry, where he has to beat up some more Greasers near a Chinese restaurant they hang out with. Finally, he has to return to Damon and receive cash for the work.
It is unknown why this mission got dummied out. Damon's dialogue makes it sound like he may have been planned as a Preppy at some point in development, but the final version of the Damon character is a Jock and has a grudge against the Preppies.
Please note that this video is a recreation.