yes, you can.
1. if you sync to your computer, turn on bookmark syncing on your mac (your icloud).
2. clear reading list on your mac.
3. turn off bookmark syncing on mac (icloud).
4. disconnect ipad from wifi or 3g network.
5. turn off bookmark syncing on ipad (icloud).
6. you'll get a message something about "do you want to delete bookmark stuff from your ipad?"
7. say "YES!" reading list will be gone!
8. connect ipad to wifi. mac bookmark syncing should be off.
your bookmarks will look different. they are there, just farther down list, so you'll have to do a bit of cleaning up (better than deleting like TEN THOUSAND reading list items one by one! I DON'T KNOW WHY APPLE THINKS YOU DESERVE A CHOICE IN DELETING YOUR HISTORY, BUT NOT YOUR READING LIST. or, in the alternative, allow easier editing the same way you can edit bookmarks. pffft.
i have spent hours on phone with apple care on this issue. nothing worked. some "fixes" really messed up my bookmarks. if you have problems in ipad safari, as in long (up to 5 or more seconds) lapse time adding link to reading list OR not being able to "mail link to this page" because email pops up and immediately greys out AND safari is frozen, a long, LONG reading list is likely the culprit.
you're welcome, apple geniuses.