Edit: I misread the question and answered what I thought you were asking, not what you actually asked.
To clone just the trunk
Cloning a single Subversion directory is easy, and it actually doesn’t matter which directory you clone. Just don’t specify any of the “layout” arguments, and give the path to the trunk directly:
git svn clone http://path.to.svn.repo/module1/trunk
To clone a specific module, including tags and branches and so forth
A “normal” git svn clone would look something like the following:
git svn clone --stdlayout http://path.to.svn.repo/
What you want to use instead will be thus:
git svn clone --stdlayout http://path.to.svn.repo/module1/
That will find the trunk, branch and tag subfolders of the module1 folder, and clone them for you.