Staple moulded artist's material (6)
I believe the answer is:
pastel
'artist's material' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I can't see?
'staple moulded' is the wordplay.
'moulded' is an anagram indicator.
'staple' is an anagram of 'PASTEL'.
Can you help me to learn more?
(Other definitions for pastel that I've seen before include "Soft shade; crayon" , "Crayon - pale colour" , "Type of crayon" , "Crayon - gentle shade of colour" , "Chalk-like crayon" .)