Very wicked act (8)
I believe the answer is:
atrocity
'very wicked act' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for atrocity that I've seen before include "villainy" , "Appalling act" , "'Barbarity, heinous act (8)'" , "Evil act" , "Barbarous, inhuman act" .)