Government department defends article on international capital (5)
I believe the answer is:
hanoi
'capital' is the definition.
(capital of Vietnam)
'government department defends article on international' is the wordplay.
'government department' becomes 'ho' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'defends' means one lot of letters goes inside another (inserted letters are held or defended).
'article' becomes 'an' (indefinite article).
'on' is a charade indicator (letters next to each other).
'international' becomes 'i' (abbreviation eg in IMF).
'ho' going around 'an' is 'hano'.
'hano'+'i'='HANOI'
Can you help me to learn more?
(Other definitions for hanoi that I've seen before include "Capital city of Vietnam" , "Vietnamese capital" , "capital out East" , "foreign city" , "Asian capital on the Red River" .)