Peru turned out to be clean (4)
I believe the answer is:
pure
'be clean' is the definition.
('pure' can be similar in meaning to 'clean')
'peru turned out' is the wordplay.
'turned out' indicates an anagram.
'peru' is an anagram of 'PURE'.
'to' is the link.
(Other definitions for pure that I've seen before include "Not mixed or adulterated" , "Unsoiled" , "Unmixed with anything else" , "Unadulterated" , "Innocent, uncontaminated" .)