Ruin, spoil (6)
I believe the answer is:
mangle
This clue is a double definition.
'ruin' is the first definition.
(I've seen this before)
'spoil' is the second definition.
(I know that mangle is a type of blemish)
(Other definitions for mangle that I've seen before include "Machine that uses rollers to press" , "Mutilate - clothes wringer" , "Wringer - make a mess of" , "Squelchy washing squasher" , "Squeeze" .)