Stops before one gives utterance to (8)
I believe the answer is:
prevents
'stops' is the definition.
(I've seen this before)
'before one gives utterance to' is the wordplay.
I cannot quite see how this works, but
'before' could be 'pre' (prefix meaning 'before') and 'pre' is found within the answer.
The remaining letters 'vents' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for prevents that I've seen before include "Blocks" , "Stops from happening" , "Keeps form happening" .)