Town decrees filth must be recycled (12)
I believe the answer is:
chesterfield
'town' is the definition.
(town in Derbyshire)
'decrees filth must be recycled' is the wordplay.
'must be recycled' is an anagram indicator.
'decrees'+'filth'='decreesfilth'
'decreesfilth' anagrammed gives 'CHESTERFIELD'.
(Other definitions for chesterfield that I've seen before include "Derbyshire town - sofa" , "Twisted-spire town; sofa" , "Part of Derbyshire" , "He wrote, advising his son" , "Heretics fled (anag) -- Derbyshire town with a crooked church spire" .)