Go on and on (4)
I believe the answer is:
rant
'go on and on' 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 "Speak wildly and incoherently" , "bombast" , "Speak intemperately" , "Intemperate speech" , "Shout wildly at length" .)