If you simply want to go back to an other revision, update is what you are looking for:
svn update -r 9
You can work on the code but you can’t commit changes. Well, if revision 10 didn’t change the same file you changed, you could commit but it’s better if you wait for revision 10 to be fixed.
Instead, if you want to go ahead and work on the code, you might consider to create a branch from revision 9, go ahead in the branch and reintegrate the branch into trunk when revision 10 is fixed.