A bad stain in fabric (5)
I believe the answer is:
satin
'fabric' is the definition.
(type of fabric)
'a bad stain' is the wordplay.
'a bad' indicates anagramming the letters.
'stain' is an anagram of 'SATIN'.
'in' acts as a link.
(Other definitions for satin that I've seen before include "Saint (anag.)" , "Stain on shiny cloth" , "Rich cloth" , "covered with?" , "Material with glossy front and dull back" .)