Decked in expensive material, scoffed about waste product (7)
I believe the answer is:
aureate
'decked in expensive material' is the definition.
Both the definition and answer are adjectives. Maybe there's an association between them I don't understand?
'scoffed about waste product' is the wordplay.
'scoffed' becomes 'ate' ('to scoff' is to eat).
'about' is an insertion indicator.
'waste product' becomes 'urea' (compound in urine).
'ate' placed around 'urea' is 'AUREATE'.
Can you help me to learn more?
(Other definitions for aureate that I've seen before include "Flowery (speech or prose)" , "Golden, brilliant" , "Gilded, elaborate" .)