Speak of nothing but speed? (5)
I believe the answer is:
orate
'speak' is the definition.
(orating is a kind of speaking)
'nothing but speed?' is the wordplay.
I cannot really see how this works, but
'nothing' could be 'o' (O resembles 0) and 'o' is present in the answer.
'speed?' could be 'rate' (the speed at which something happens) and 'rate' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'of' acts as a link.
Can you help me to learn more?
(Other definitions for orate that I've seen before include "Declaim or rant" , "Give speech" , "Harangue" , "Make a lengthy speech" , "Spout" .)