Agree with everything BFB said above. Also, a minor but salient point: in interviews, conversations, etc., never pitch your clerkship experience as an asset that counterbalances your grades. You're not compensating for what you did in law school -- this isn't a tit for tat exchange.
Phrases like "at least," "but," "luckily," etc. will all convey that you know you have some bad history behind you and you're eager to whitewash with your future actions. And that kind of attitude may come across as defensive or weak. Also, it encourages people to draw false and ridiculous comparisons (e.g., arbitrarily deciding that a clerkship "excuses" three Cs, or something equally inapt).
Draw a firm line between your academic career and your professional career. While you may have struggled in law school (due to XYZ reasons), make it clear that you have NEVER struggled professionally. Your work product is excellent, your demeanor professional, your skill set is well above your peers, and you have the respect and admiration of judges and seasoned attorneys. You know what you want, you go after it, and you're a success.
Pay homage to the profession and your career goals; explain that your success now is because you're in your element, in a way that you weren't during law school. "The thing I was bad at, back then? It required particular skills, which I didn't have at the time. The things I'm good at now? They require these particular skills, which I have in abundance and which you really want."
By your attitude, your word choice, and your general confidence, you can indicate to colleagues and potential employers that you don't think you need to "make up" for your poor performance back then. That was then -- a different place, a different beast. School really is completely different from the working world. You are a success in ONE of those arenas. In the other, you didn't do as well as you would've liked. Oh, well.
Even attorneys who did well in school (and who may be skeptical of your XYZ reasons) will still approve heartily of the maturity of your perspective. They all know that law school doesn't prepare a person for legal practice, and obviously they're all in legal practice now. So, play up to their ego and to your strengths: tell them that what they're doing now, which they're obviously proud of, is what you're good at and what you want to do.