Peru turned out to be unsullied (4)
I believe the answer is:
pure
'to be unsullied' is the definition.
(I've seen this before)
'peru turned' is the wordplay.
'turned' indicates anagramming the letters.
'peru' with letters rearranged gives 'PURE'.
'out' is the link.
(Other definitions for pure that I've seen before include "Unadulterated" , "Unalloyed" , "Chaste" , "Virgin" , "Flawless, unsullied" .)