Life force embodied by Achilles? (3)
I believe the answer is:
chi
'life force' is the definition.
(I've seen this in another clue)
'embodied by achilles?' is the wordplay.
'embodied by' indicates a hidden word.
'CHI' can be found hidden inside 'achilles'.
(Other definitions for chi that I've seen before include "Chinese life-force" , "In Chinese medicine, the life force inherent in all things" , "The 22nd letter of Greek alphabet" , "Greek letter; force in Chinese philosophy" , "Twenty-second Greek letter" .)