Stylish address, like uppity, nastier town centre (6,3)
I believe the answer is:
savile row
'stylish address' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'like uppity nastier town centre' is the wordplay.
'like' becomes 'as'.
'uppity' says the letters should be written in reverse (in a down clue, words go 'up').
'nastier' becomes 'viler' ('vile' can be a synonym of 'nasty').
'town centre' becomes 'ow' (central letters of the word 'town').
'as' written backwards gives 'sa'.
'sa'+'viler'+'ow'='SAVILE ROW'
Can you help me to learn more?
(Other definitions for savile row that I've seen before include "London tailors' street" , "Street noted for tailoring" , "London's tailoring street" , "Fitting way" , "Well-known street" .)