Twigs evil must finally change (6)
I believe the answer is:
wicker
'twigs' is the definition.
(material made from twigs)
I don't understand how the remainder of the clue works.
(Other definitions for wicker that I've seen before include "Willow shoot (work)" , "Plaited or woven twigs" , "Pliant twig, osier" , "Made of flexible twigs" , "Thin canes woven together as material" .)