Eccentric late aunt's land (9)
I believe the answer is:
sultanate
'land' is the definition.
(thesaurus)
'eccentric late aunt's' is the wordplay.
'eccentric' is an anagram indicator.
'late'+'aunts'='lateaunts'
'lateaunts' anagrammed gives 'SULTANATE'.
(Other definitions for sultanate that I've seen before include "Brunei?" , "Country" , "Muslim dominion" , "Turkey was" .)