Speak grandiloquently (5)
I believe the answer is:
orate
'speak grandiloquently' 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 "Make a flowery speech" , "Erato (anag.)" , "Speak formally" , "Speak publicly" , "Speak like Cicero?" .)