Country, say, unknown part (5)
I believe the answer is:
egypt
'country' is the definition.
(Egypt is an example)
'say unknown part' is the wordplay.
'say' becomes 'eg'.
'unknown' becomes 'y' (algebra).
'part' becomes 'pt' (I've seen this in other clues).
'eg'+'y'+'pt'='EGYPT'
(Other definitions for egypt that I've seen before include "Cleopatra's country" , "Country of pyramids" , "Country ruled by Cleopatra" , "Cairo's country" , "Republic of North Africa" .)