Doctor getting behind plan (5)
I believe the answer is:
draft
'plan' is the definition.
(drafting is a kind of planning)
'doctor getting behind' is the wordplay.
'doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor').
'getting' says to put letters next to each other.
'behind' becomes 'aft' ('aft' can be a synonym of 'behind').
'dr'+'aft'='DRAFT'
(Other definitions for draft that I've seen before include "Preliminary text or plan" , "book's outline" , "select group" , "Written plan" , "Rough drawing" .)