Time Machine should be able to do it if you have a pre-upgrade backup date available. Otherwise you probably have to reinstall the older OS on a fresh drive (for safety, so you can go back if things go wrong - which don't as much on OSX) then use Migration Assistant to move your data and settings, and selected apps (not the one that's too new) to the new imaged OS.
I've gone backwards on OS installs with that method a couple times,
I've gone backwards on OS installs with that method a couple times,