Spoil or ruin (6)
I believe the answer is:
mangle
I believe this clue is a double definition.
'spoil' is the first definition.
(I know that mangle is a type of blemish)
'ruin' is the second definition.
(I've seen this before)
(Other definitions for mangle that I've seen before include "Laundry squeezer" , "Mutilate - clothes wringer" , "Clothes-squeezer" , "Old-fashioned clothes dryer" , "rolling-press" .)