I'm not sure if this is what you mean, but if your goal is to selectively convert some of the smooth transitions to sharp transitions, you can do this either by adding additional Geometry (often through loop cuts, as shown here):
(note: sharpness depends on how close the new loop cut is to the old loop cut, because the subdivision surface adds geometry between them -- hence, if there is no or little space between them, the subdivision surface has little or nothing to smooth)
Which results in:
And/or by using Mark Seam: Sharp
(result not pictured)
If, instead, you want to remove some of the undesired unevenness of the mesh or something else, a different answer/solution will be needed.