Antelope's endless spirit (4)
I believe the answer is:
'spirit' is the definition.
(I know that elan is a type of life)
'antelope's endless' is the wordplay.
'antelope' becomes 'eland' (eland is a kind of antelope).
'endless' means to remove the last letter.
'eland' with its last letter removed is 'ELAN'.
(Other definitions for elan that I've seen before include "Snap" , "fizz" , "Vitality" , "Panache - ardour" , "French verve" .)