Who took Helen's capital? (5)
I believe the answer is:
paris
I believe this clue is a double definition.
'who took helen's' is the first definition.
(Paris stole Helen of Troy away in Greek myth)
'capital?' is the second definition.
(Paris is the capital of France)
(Other definitions for paris that I've seen before include "investment resulted from his action" , "City on the Seine" , "European capital city" , "Legendary prince" , "Prince who abducted Helen, starting a long war (see 8)" .)