You can try to do both basic science research and clinical volunteer work. Don't go crazy with the volunteer work, if you shadow a physician once per week for a month or two, that should be sufficient. If you are sure that you want to go into medicine, just get any random clinical experience that doesn't require a lot of time. On that note, if you are able to get some good experience, you can incorporate it into your personal statement so be sure to be on the look out for good stories while you are volunteering. You can do your volunteer work on Fridays or something instead of going into the lab, most lab PIs are very flexible with undergrads. Just make sure that you do meaningful research in the lab (not washing beakers 24/7, beaker washing is OK sometimes), and that you get paid (you will need a lot of $$ for the application process).