Dark wicked thing (5)
I believe the answer is:
night
'dark' is the definition.
(night is a kind of dark)
'wicked thing' is the wordplay.
'wicked' indicates anagramming the letters.
'thing' with letters rearranged gives 'NIGHT'.
(Other definitions for night that I've seen before include "follow-up to 16 [TWILIGHT]" , "Saturday -- Fever (film)" , "Ignorance" , "Tennyson's "black bat"" , "Time between days" .)