Cause to go "Vroom!" (3)
I believe the answer is:
rev
'cause to go vroom' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rev that I've seen before include "Reverend (abbr.)" , "Motor rotation, in short" , "Accelerate (abbrev.)" , "In engine-room speed up" , "Speed up engine (colloq.)" .)