Clean Up Contour > Clean Up attempts to remove unnecessary nodes from your outlines. It will do so by approximating a segment of the contour with a curve. It differs from Simplify in that it will not add new nodes to your contours; and will be less aggressive in removing points, therefore keeping the contour shape closer to the original.
This operation can be applied to a single glyph if it is open in the Glyph Window, or you can select several glyphs in the Font Window or Font Map panel and run the operation on all of them together. Apart from the Contour menu, this operation is also found in Contour actions in ==Tools > Actions=.