Row about doctor breaking a regulation (6)
I believe the answer is:
rumble
'row' is the definition.
(thesaurus)
'doctor breaking a regulation' is the wordplay.
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'breaking' means one lot of letters goes inside another.
'a regulation' becomes 'rule' (synonyms).
'mb' going inside 'rule' is 'RUMBLE'.
'about' is the link.
(Other definitions for rumble that I've seen before include "Low continuous noise" , "Utter in deep voice, of have a slang fight - in the jungle?" , "Harlem gangs might" , "Tummy sound - discover (an illicit activity)" , "Sound of thunder or a hungry stomach - discover (plans)" .)