End of European country after a Nationalist defects (6)
I believe the answer is:
finish
'country after a nationalist defects' is the definition.
I can't judge whether this definition defines the answer.
'end of european' is the wordplay.
'end of' means to remove the middle letters (I've seen 'ends' mean this).
'european' becomes 'finnish'.
'finnish' with its centre removed is 'FINISH'.
(Other definitions for finish that I've seen before include "End, conclusion" , "Refinement in social graces" , "Bring to an end" , "Pefect" , "Complete (6,3) - See 16" .)