Prep for dragging (3)
I believe the answer is:
rev
'prep for dragging' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rev that I've seen before include "Clergyman, or woman (abbr)" , "Accelerate (abbrev.)" , "Clergy title" , "Speed up engine (colloq.)" , "serviceman?" .)