If you mean the trapezoidal shaped one on the rear edge by the wheel arch you should be able to get to it by undoing the clips down the wheel arch and then reaching in. You'll likely lose the centre pins of the clips.
You may need to separate the top of the bumper cover from the metal wing by pulling it out.
The reflector is It's held by 2 self tapping nuts on plastics pins on the reflector.
Personaly I'd simply pull off the entire side of the bumper by unbolting along the top edge and bottom and swing it out 6"
