You almost sussed out Greek hero (8)
I believe the answer is:
odysseus
'greek hero' is the definition.
(I've seen this before)
'you almost sussed out' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'you' with its final letter taken away is 'yo'.
'yo'+'sussed'='yosussed'
'yosussed' is an anagram of 'ODYSSEUS'.
(Other definitions for odysseus that I've seen before include "Gr. hero, aka Ulysses" , "Classical traveller" , "Greek name for Ulysses" , "Legendary hero" , "Voyager" .)