I had one too a couple of days ago but when i clicked on the link it displayed page error and my ebay has still been fine. You'll know if someone has tried to clone your account cos there will be stuff in MY EBAY that you will not have bought. I think there was a thing going around about a bogus email being sent to you to try and get you to re enter your account details so they could clone you which is ironic as the email is warning you about being cloned!!!!!
I emailed ebay about this and never got a reply!!!!!!!!!!!