You have to select part of the skin layer (located in the Ctl+V box) and right clock within the box and select the Ctrl+S option. Then select YES when the pop up asks if you really want to create a new layer. After you've created the new layer you will see a new layer has appeared in the Ctrl+V box labeled "Nw". Right click on this layer and select the Ctrl+P option which will delete the said under skin that is showing through the clothing!
I learned this myself courtesy of . Go to their profile and gallery if you want to check out their tutorial on clothing application! Hope I helped~