More evil packing material, unopened (5)
I believe the answer is:
iller
'more evil' is the definition.
(ill can mean evil or wrong)
'packing material unopened' is the wordplay.
'packing material' becomes 'filler' (material used when packaging something up).
'unopened' means to remove the first letter (without opening letter).
'filler' with its initial letter removed is 'ILLER'.
(Other definitions for iller that I've seen before include "Less well" , "Even more 9" , "In worse health" .)