Rich and posh MP turned out in southern states? (9)
I believe the answer is:
sumptuous
'rich' is the definition.
(similar in meaning)
'posh mp turned out in southern states?' is the wordplay.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'turned' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'southern' becomes 's' (abbreviation).
'states?' becomes 'us' (abbreviation for the United States).
'out' reversed gives 'tuo'.
'u'+'mp'+'tuo'='umptuo'
's'+'us'='sus'
'umptuo' placed into 'sus' is 'SUMPTUOUS'.
'and' is the link.
(Other definitions for sumptuous that I've seen before include "Delicious and expensive" , "Expensive-looking, splendid" , "Grand" , "Luxurious" , "Splendid, rich" .)