Athenian statesman replies unexpectedly about leader of country (8)
I believe the answer is:
pericles
'athenian statesman' is the definition.
(I've seen this before)
'replies unexpectedly about leader of country' is the wordplay.
'unexpectedly' indicates an anagram.
'about' indicates putting letters inside.
'leader of' says to take the initial letters.
The initial letter of 'country' is 'c'.
'replies' anagrammed gives 'periles'.
'periles' enclosing 'c' is 'PERICLES'.
(Other definitions for pericles that I've seen before include "Athenian 'golden age' leader" , "Statesman in Athens" , "Athenian statesman" , "Ancient Athenian leader - prince of Tyre" , "Shakespearean play" .)