Northern diner more elegant (6)
I believe the answer is:
neater
'more elegant' is the definition.
('neat' can be similar in meaning to 'elegant')
'northern diner' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'diner' becomes 'eater' (I've seen this before).
'n'+'eater'='NEATER'
(Other definitions for neater that I've seen before include "approaching apple-pie order" , "Better" , "Tidier" , "Less messy" , "More tidy and orderly" .)