The satin's spoiled by the marks (6)
I believe the answer is:
stains
'the marks' is the definition.
('stain' can be a synonym of 'mark')
'the satin's spoiled' is the wordplay.
'spoiled' indicates anagramming the letters.
'satins' is an anagram of 'STAINS'.
'by' is the link.
(Other definitions for stains that I've seen before include "Sullies" , "Discolorations or dirt marks" , "Dirty marks" , "Discolourations on satins" , "Discolours or dyes wood" .)