Bitter outburst (6)
I believe the answer is:
tirade
'bitter outburst' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tirade that I've seen before include "A prolonged diatribe" , "Vocal abuse" , "Prolonged abusive speech" , "Inclination; fish" , "A long, vehement harangue" .)