Yes, renaming the virus usually makes it unaccessable to any other software that wants to use it, as does putting it in the quarantine folder also. Verify that the file does actually contain a virus--upload it to Jotti at http://virusscan.jotti.org/
on the web or to VirusTotal at http://www.virustotal.com/
on the web to have it scanned for free to verify it's infected. If several antiviruses (besides Clam) at one of these services find it's infected, it's probably a real infection and not a false positive, and you can safely delete it manually from the quarantine folder.
If it turns out to be a false positive, tell Clam about it at http://cgi.clamav.net/sendvirus.cgi
on the web. Be sure to check the false positive block, and put the exact name Clam spots it as, and indicate "false positive" in the description area. Then you can rename the file and put it back in the directory Where ClamWin found it. False positives are usually removed from Clam's signatures a day or so after they find out about it.