Aristocratic children's doctor must dismiss aide from the east (9)
I believe the answer is:
patrician
'aristocratic' is the definition.
('patrician' can be a synonym of 'aristocratic')
'children's doctor must dismiss aide from the east' is the wordplay.
'children's doctor' becomes 'paediatrician'.
'must dismiss' is a deletion indicator.
'from the east' says the letters should be written backwards.
'aide' back-to-front is 'edia'.
'paediatrician' with 'edia' taken away is 'PATRICIAN'.
(Other definitions for patrician that I've seen before include "belonging to the aristocracy" , "Upper-class" , "Perhaps senator <" , "aristocratic" , "Roman nobleman" .)