If it has been more than 10 days since it started seeding you will likely have some volunteer BW come up in that plot. So, the answer to your question is yes, if you mow it will re-sprout within the next couple weeks. We never found it to be an issue on our place, as we welcomed free seed. It will die after the first frost or two either way. I agree with bueller, just use that leftover wr, rc, and add some GHR. Broadcast and roll. Done deal. That red clover is free N waiting to happen. Next spring you can choose to let the rye and clover go and have a good clover stand with free reseeded rye, or you could mow the rye before it sets seed and have a straight clover plot until you are ready to move forward with your orchard plans. You also have the option to terminate the rye with clethodim and have a grass free clover plot.