Hero fell, captured by champions (8)
I believe the answer is:
achilles
'hero' is the definition.
(I've seen this before)
'fell captured by champions' is the wordplay.
'fell' becomes 'hill' (I've seen this before).
'captured by' means one lot of letters goes inside another.
'champions' becomes 'aces' (I've seen this before).
'hill' inserted inside 'aces' is 'ACHILLES'.
(Other definitions for achilles that I've seen before include "Greek hero who slew Hector" , "Greek hero with a weak point" , "Weak-heel warrior" , "Greek hero (with heel and tendon)" , "His heel was his weak point" .)