Used soy sauce primarily for cooking Greek on epic journey (8)
I believe the answer is:
odysseus
'greek on epic journey' is the definition.
(Odysseus went on an epic journey)
'used soy sauce primarily for cooking' is the wordplay.
'primarily' suggests taking the first letters.
'for cooking' indicates anagramming the letters (letters prepared or cooked into a new form).
The initial letter of 'sauce' is 's'.
'used'+'soy'+'s'='usedsoys'
'usedsoys' with letters rearranged gives 'ODYSSEUS'.
(Other definitions for odysseus that I've seen before include "King of Ithaca, who returned after the siege of Troy" , "Greek hero of an epic journey home from Troy" , "Homer's mythical Greek hero" , "Legendary hero" , "Gr. hero, aka Ulysses" .)