Capital founded as Ciudad de los Reyes (4)
I believe the answer is:
lima
'capital founded as ciudad de los reyes' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lima that I've seen before include "South American capital" , "Peruvian capital" , "Send mail out to S America" , "distant city" , "Mail to capital of Peru" .)