Cloth’s unfortunate stain (5)
I believe the answer is:
satin
'cloth's' is the definition.
(satin is a kind of cloth)
'unfortunate stain' is the wordplay.
'unfortunate' indicates anagramming the letters.
'stain' is an anagram of 'SATIN'.
(Other definitions for satin that I've seen before include "Stain on silky cloth" , "Silky material" , "Rich cloth" , "Stain on shiny fabric" , "covered with?" .)