Seems like the closet thing to Minus Front Fontlab has is Delete Intersection. Which sometimes works like Minus Front, and sometimes doesn't. In this pic I have drawn a crude shape on top of the t's ascender with the intent of only using it to chop away at the t. Both the shapes are highlighted in red in the first pic. Most vector programs have a Minus Front feature which would simply trim the area of overlap and the entire object on top. When I tired Delete Intersection in the example here, however, the result was a separate shape for the overlap, and a separate shape for the outline of both object. I have the combined outline shape selected and it appears in red in the second pic.