I'm not sure what you're trying to do: If you added the file via
svn add myfile
you only told svn to put this file into your repository when you do your next commit. There's no change to the repository before you type an
svn commit
If you delete the file before the commit, svn
has it in its records (because you added it) but cannot send it to the repository because the file no longer exist.
So either you want to save the file in the repository and then delete it from your working copy: In this case try to get your file back (from the trash?), do the commit and delete the file afterwards via
svn delete myfile
svn commit
If you want to undo the add
and just throw the file away, you can to an
svn revert myfile
which tells svn
(in this case) to undo the add-Operation.
EDIT
Sorry, I wasn't aware that you're using the "Versions" GUI client for Max OSX. So either try a revert on the containing directory using the GUI or jump into the cold water and fire up your hidden Mac command shell :-) (it's called "Terminal" in the german OSX, no idea how to bring it up in the english version...)