Difference between to become clean and to be smooth in Korean
깨끗해지다·매끄럽다

깨끗해지다to become clean
깨끗해지다 means "to become clean." Use it when something changes from dirty to clean, like a room, clothes, or a street after rain. You can use it for many everyday things and places.

매끄럽다to be smooth
매끄럽다 means something is smooth, not rough, and feels nice to touch. You can use it for surfaces like skin, stone, or a desk. It can also describe movement, speech, or a process that goes smoothly without problems.
The difference
깨끗해지다 means dirt or mess is removed. Something can be clean but still not smooth to the touch.