Broken tree root
A strong wind blew a 10 foot tall red oak tree over against a fence breaking one of the main roots but the others appear to be intact. If the tree is braced back in it's original position will the root grow new shoots making the tree stable again?
It might be possible to salvage the tree. The best way to find out is to ask a certified arborist or forester to assess the situation onsite and recommend a course of action.
If you decide to hire an arborist, the following information may be of interest:
How to hire a professional arborist to help care for your landscape trees
Although information in the following bulletins mostly applies to trees larger than the one you described, the principles are relevant to your tree too.