Sounds like this D is on your HS transcript? If so, how will the retake show up on your transcript? What grade did you get on the retake?
If the D remains on the transcript after the retake, I would have your HS counselor address the 8th grade D and the retake with the grade in their rec letter. You can also address it in the common app addt’l info section, but keep it short and factual (but it’s relatively more important to have your counselor address it).