Make the speech that’s longest and greatest (9)
I believe the answer is:
uttermost
'greatest' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for uttermost that I've seen before include "at the furthest limit" , "Chief" , "The furthest point or degree" , "Extreme" , "best" .)