Speak from a soapbox (5)
I believe the answer is:
orate
'speak from a soapbox' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for orate that I've seen before include "Declaim or rant" , "Speak publicly" , "Speak like Cicero?" , "Speak pompously and at length" , "Make a flowery speech" .)