Bygone Peruvians (5)
I believe the answer is:
incas
'bygone peruvians' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for incas that I've seen before include "Old people coming from South America" , "Ancient Peruvians" , "Peruvian natives" , "Members of ancient Peruvian race" , "Old Peruvians" .)