Mark ruined satin (5)
I believe the answer is:
stain
'mark' is the definition.
('stain' can be a synonym of 'mark')
'ruined satin' is the wordplay.
'ruined' indicates an anagram.
'satin' is an anagram of 'STAIN'.
(Other definitions for stain that I've seen before include "Blemish; colour (wood)" , "Discolouration" , "Discoloured mark" , "Mark with colour, dirt" , "Unsightly mark" .)