Experts going over high ground to find Greek hero (8)
I believe the answer is:
achilles
'greek hero' is the definition.
(I've seen this before)
'experts going over high ground' is the wordplay.
'experts' becomes 'aces' (ace is a kind of expert).
'going over' means one lot of letters goes inside another.
'high ground' becomes 'hill' (I've seen this before).
'aces' going around 'hill' is 'ACHILLES'.
'to find' acts as a link.
(Other definitions for achilles that I've seen before include "Legendary Greek with injured heel" , "Warrior of old" , "Heroic warrior" , "Greek hero who gave his name to a bad heel" , "Legendary Greek with bad heel" .)