Energy-packed NCO material (9)
I believe the answer is:
corporeal
'material' is the definition.
('corporeal' can be a synonym of 'material')
'energy-packed nco' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'packed' indicates putting letters inside (some letters are packed into others).
'nco' becomes 'corporal' (I've seen this before).
'e' placed inside 'corporal' is 'CORPOREAL'.
(Other definitions for corporeal that I've seen before include "Bodily" , "physical" , "pink material" , "not spiritual" , "of flesh" .)