Plan drive to the rear (5)
I believe the answer is:
draft
'plan' is the definition.
(drafting is a kind of planning)
'drive to the rear' is the wordplay.
'drive' becomes 'dr' (I've seen this in other clues).
'to the rear' becomes 'aft' (I've seen this before).
'dr'+'aft'='DRAFT'
(Other definitions for draft that I've seen before include "Current of air or preliminary sketch" , "Sketch; money order" , "Sketch - detachment of men" , "plan outlined" , "A money order for US conscription" .)