Doctor, I have an urge (5)
I believe the answer is:
drive
'an urge' is the definition.
(I've seen this before)
'doctor i have' is the wordplay.
'doctor' becomes 'dr' ('Dr' can be a synonym of 'doctor').
'i have' becomes 'ive' (**).
'dr'+'ive'='DRIVE'
(Other definitions for drive that I've seen before include "zip" , "natural urge" , "Hit golf ball from tee" , "Go by car" , "Trip in car - road to house" .)