Once you start fiddling with your Samsung Galaxy Tab 3 7.0 and for some reason, something goes wrong with your tablet, you might want to restore it to its original stock firmware. This will remove the custom clockwork mod, custom ROM, kernels and so on.
Basically, your tablet will become just like the way it was when you opened its box for the first time. So, download the ROM from here; put your Galaxy Tab 3 7.0 in download mode (vol down + power for few seconds); connect it to your computer and using the ODIN to flash it.
After that, disconnect your Samsung mini tablet from the computer and set it up again.