Peloponnesian War victor (6)
I believe the answer is:
sparta
'peloponnesian war victor' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sparta that I've seen before include "in ancient Greece" , "it was a hard place" , "Ancient Greek city synonymous with austerity" , "Ancient Greek city noted for tough citizens" , "Ancient Greek city noted for its austerity" .)