Vent vocally (4)
I believe the answer is:
rant
'vent vocally' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rant that I've seen before include "bombast" , "Wild speech" , "Loud and emotional declamation" , "Angry outburst" , "Speak wildly and incoherently" .)