From south, excellent railway going to the North Country (5)
I believe the answer is:
syria
'country' is the definition.
(Syria is an example)
'from south excellent railway going to the north' is the wordplay.
'from south' becomes 'sy' (I can't justify this - if you can you should give a lot more credence to this answer).
'excellent' becomes 'ai'.
'railway' becomes 'r' (eg in Great Western Railway).
'going to the north' says the letters should be written in reverse (in a down clue, letters go up).
'ai'+'r'='air'
'air' back-to-front is 'ria'.
'sy'+'ria'='SYRIA'
(Other definitions for syria that I've seen before include "Middle-Eastern country" , "West Asian Republic" , "Antioch once its capital" , "Arab republic, independent since 1946" , "Eastern Mediterranean country" .)