Ain't leaving great-niece in the union (6)
I believe the answer is:
greece
'the union' is the definition.
The definition and answer can be both locations as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'ain't leaving great-niece' is the wordplay.
'leaving' is a deletion indicator.
'great'+'niece'='greatniece'
'greatniece' with 'aint' taken away is 'GREECE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for greece that I've seen before include "Hellenic republic" , "Mediterranean republic" , "Country of Aristotle and Plato" , "Country of Sophocles and Aristotle" , "Country of Hellenes" .)