Everyone's included in wicked song (6)
I believe the answer is:
ballad
'song' is the definition.
(I know that ballad is a type of song)
'everyone's included in wicked' is the wordplay.
'everyone' becomes 'all' (all people).
'included in' is an insertion indicator.
'wicked' becomes 'bad' (associated in meaning).
'all' inserted inside 'bad' is 'BALLAD'.
(Other definitions for ballad that I've seen before include "Slow sentimental song" , "romance" , "delivered by singer" , "Narrative song with a recurrent refrain" , "Slow romantic song" .)