Expense initially invested in NCO material (9)
I believe the answer is:
corporeal
'material' is the definition.
('corporeal' can be a synonym of 'material')
'expense initially invested in nco' is the wordplay.
'initially' indicates taking the first letters.
'invested in' indicates putting letters inside.
'nco' becomes 'corporal' (I've seen this before).
The initial letter of 'expense' is 'e'.
'e' going within 'corporal' is 'CORPOREAL'.
(Other definitions for corporeal that I've seen before include "physical" , "of flesh" , "pink material" , "not spiritual" , "Bodily" .)