Tune everyone critical about (6)
I believe the answer is:
ballad
'tune' is the definition.
(type of song)
'everyone critical about' is the wordplay.
'everyone' becomes 'all' (all people).
'critical' becomes 'bad' (critical can mean dangerous or bad).
'about' is an insertion indicator.
'all' put within 'bad' is 'BALLAD'.
(Other definitions for ballad that I've seen before include "Narrative song of popular origin" , "Simple song or poem" , "Song type" , "Narrative song with a recurrent refrain" , "Slow sentimental song" .)