Peru turned out to be perfect (4)
I believe the answer is:
pure
'be perfect' is the definition.
('pure' can be a synonym of 'perfect')
'peru turned out' is the wordplay.
'turned out' indicates anagramming the letters.
'peru' with letters rearranged gives 'PURE'.
'to' acts as a link.
(Other definitions for pure that I've seen before include "Innocent; not mixed" , "Virginal" , "Untainted" , "Innocent; unsullied" , "Undefiled" .)