Cast to include unusual material (poor stuff) (6)
I believe the answer is:
shoddy
'material poor stuff' is the definition.
(type of low-quality fabric)
'cast to include unusual' is the wordplay.
'cast' becomes 'shy' (I've seen this before).
'to include' means one lot of letters goes inside another.
'unusual' becomes 'odd' (similar in meaning).
'shy' placed around 'odd' is 'SHODDY'.
(Other definitions for shoddy that I've seen before include "Kind of worsted" , "Badly engineered" , "clippings in this" , "poor quality fabric" , "Poor-quality" .)