Adore old ruined city that's fabulously rich (2,6)
I believe the answer is:
el dorado
'city that's fabulously rich' is the definition.
(mythical city of gold)
'adore old ruined' is the wordplay.
'ruined' indicates anagramming the letters.
'adore'+'old'='adoreold'
'adoreold' anagrammed gives 'EL DORADO'.
(Other definitions for el dorado that I've seen before include "Place of great wealth, from fictitious city on the Amazon" , "Place of fabulous opportunity" , "Land of great wealth" , "Lead door (anag) - the land of gold!" , "Imaginary land of riches" .)