Upgrading a single package is often not a problem. Upgrading libc will be. There are simply too many other packages that depend on it:
$ apt-cache rdepends libc6 |wc
16057
That means that 16057 other packages will depend on libc6 and some of them are bound to have problems with the new version. That's one of the main benefits of a packaging system.
So, you don't want to upgrade that without upgrading the rest of your system. What you could do is create a chroot environment and install a minimal distribution there. For details on how to do that, have a look at @Gilles's answers here: