Phrase too much adopted by doctor? (5)
I believe the answer is:
motto
'phrase' is the definition.
(thesaurus)
'too much adopted by doctor?' is the wordplay.
'too much' becomes 'ott' (short for 'over the top' - informal British).
'adopted by' is an insertion indicator (I've seen this in other clues).
'doctor?' becomes 'mo' (medical officer).
'ott' going within 'mo' is 'MOTTO'.
(Other definitions for motto that I've seen before include "Shibboleth" , "It may be proverbial" , "Saying in a cracker" , "cry" , "statement of belief" .)