Discover doctor breaching guideline (6)
I believe the answer is:
rumble
'discover' is the definition.
(to rumble someone is to discover their secret)
'doctor breaching guideline' is the wordplay.
I cannot quite understand how this works, but
'doctor' could be 'mb' (Bachelor of Medicine, Medicinae Baccalaureus) and 'mb' is found in the answer.
'guideline' could be 'rule' (I've seen this in another clue) and 'rule' is found within the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rumble that I've seen before include "Carriage seat gives the sound of heavy wheels" , "be wise to" , "uncover secrecy perhaps" , "Fight between rival gangs of adolescents" , "Tummy sound - discover (an illicit activity)" .)