Interfere with doctor in case (6)
I believe the answer is:
molest
'interfere with' is the definition.
(I've seen this before)
'doctor in case' is the wordplay.
'doctor' becomes 'mo' (medical officer).
'in case' becomes 'lest' (I've seen this in another clue).
'mo'+'lest'='MOLEST'
(Other definitions for molest that I've seen before include "Handle roughly, torment" , "Pester; assault" , "trouble" , "Fame" , "Bug" .)