Doctor Bear felt intern to be a brat (6,8)
I believe the answer is:
enfant terrible
'a brat' is the definition.
(thesaurus)
'doctor bear felt intern' is the wordplay.
'doctor' is an anagram indicator.
'bear'+'felt'+'intern'='bearfeltintern'
'bearfeltintern' anagrammed gives 'ENFANT TERRIBLE'.
'to be' is the link.
(Other definitions for enfant terrible that I've seen before include "one that causes embarrassment" , "Difficult issue in France" , "scamp" , "One behaving controversially" , "wild child - with 30a" .)