To say something extreme (5)
I believe the answer is:
utter
I believe this clue is a double definition.
'to say something' is the first definition.
(I've seen this in another clue)
'extreme' is the second definition.
(I've seen this before)
(Other definitions for utter that I've seen before include "Speak; completely" , "Complete; absolute" , "Express audibly" , "Make (a sound); complete" , "Prize" .)