First-of-all, Safari will not work properly on Xubuntu.
There is IE4Linux which is supposed to work with.
And why would you want to use Safari when there are some other good browsers?
And talking about windows installation, if you want only some of the windows softwares to use then why installing complete Windows OS when there is Crossover. Here is the link check this out:
And if this is not what you want then the simple solution is install virtual machine on your Xubuntu and install Windows on that virtual machine.
How do I install a program (Safari) into WINE
Check this page: