Monarchy, British one, stuck with old German character (6)
I believe the answer is:
brunei
'monarchy' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'british one stuck with old german character' is the wordplay.
'british' becomes 'br' (abbreviation for British).
'one' becomes 'un' (northern English dialect form of 'one').
'stuck with old german character' becomes 'ei' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'br'+'un'+'ei'='BRUNEI'
Can you help me to learn more?
(Other definitions for brunei that I've seen before include "Far Eastern sultanate" , "E. Indies sultanate" , "Ill" , "Commonwealth member" , "major source of oil" .)