Deliver a tirade (4)
I believe the answer is:
rant
'deliver a tirade' is the definition.
(a tirade is a rant)
This is all the clue.
(Other definitions for rant that I've seen before include "bombast" , "Shout wildly at length" , "Rail" , "Talk wildly, rave" , "Talk wildly, harangue" .)