In a wicked manner (6)
I believe the answer is:
evilly
'in a wicked manner' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for evilly that I've seen before include "in a bad way" , "In wicked or depraved way" , "Extremely wickedly" , "With wicked intent" , "In a very wicked manner" .)