Stained form as a substitute (7)
I believe the answer is:
'as a substitute' is the definition.
(I've seen this before)
'stained form' is the wordplay.
'form' indicates an anagram.
'stained' anagrammed gives 'INSTEAD'.
(Other definitions for instead that I've seen before include "In place (of)" , "for a change" , "as an alternative option" , "Rather - detains (anag)" , "In lieu" .)