I use a lot of fusible web for pattern design and my own creative work. I also have a very good Rowenta iron........sometime the two do not play well together. So run to your cleaning cupboard or local shop and buy a package of Magic Erasers:
Then watch this YouTube video from Sharon Schamber, where she shows just how to clean your iron with the eraser. I like to have a folded towel under the eraser to soak up any water.
Have fun enjoying your very clean iron!