Liquid underneath clotted cream
Every recipe I've ever seen for homemade clotted cream has mentioned that layer under the clotted cream.  

Clotted cream is essentially clotted milk solids (similar to butter or cheese, but obviously made quite different, and with a different taste), and the leftover liquid is analogous to the whey left over from cheese making or the liquid that remains after churning cream into butter.  

It's likely that using a higher fat content or raw (as in fresh from the cow this morning) cream may result in less leftover liquid, but I've never tried it to be sure-- perhaps someone with more experience can tell us.