Hero fell among stars (8)
I believe the answer is:
achilles
'hero' is the definition.
(I've seen this before)
'fell among stars' is the wordplay.
'fell' becomes 'hill' (I've seen this before).
'among' indicates putting letters inside.
'stars' becomes 'aces' ('ace' can be a synonym of 'star').
'hill' going into 'aces' is 'ACHILLES'.
(Other definitions for achilles that I've seen before include "Weak-heel warrior" , "7 Calf/heel connector" , "Mythical hero, vulnerable only through his heel" , "Cause of Hector's death" , "Ancient Greek hero" .)