Song composed in Athens, say (3,6)
I believe the answer is:
sea shanty
'song' is the definition.
(song sung at sea)
'composed in athens say' is the wordplay.
'athens say' anagrams to 'SEA SHANTY'.
Though, I'm not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for sea shanty that I've seen before include "A certain air" , "Traditional song sung by sailors" .)