One for suppressing reports on driving? (8)
I believe the answer is:
silencer
'one' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
I cannot understand how the rest of the clue works.
(Other definitions for silencer that I've seen before include "I keep report quiet" , "Device to muffle sound of gun" , "that back-seat drivers will ignore" , "Reclines with sound-muffling device" , "Device which quietens a car or gun" .)