Remain at odds over a nation (7)
I believe the answer is:
armenia
'nation' is the definition.
(I have seen 'Transcaucasian nation ' mean 'armenia' so perhaps 'nation' could also mean 'armenia')
'remain at odds over a' is the wordplay.
'at odds' indicates anagramming the letters.
'over' means one lot of letters go next to another.
'remain' anagrammed gives 'armeni'.
'armeni'+'a'='ARMENIA'
(Other definitions for armenia that I've seen before include "Republic in N W Asia" , "Republic formerly in the USSR" , "South-west Asian country, capital Yerevan" , "Transcaucasian nation" , "Landlocked country of southwest Asia" .)