Odyssey peak (4)
I believe the answer is:
ossa
'odyssey peak' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ossa that I've seen before include "famous mount" , "So as to turn to bones" , "Technical name for bones" , "Legendary mountain" , "To pile Pelion upon - is to make even greater" .)