Soul; life force (6)
I believe the answer is:
spirit
This clue is a double definition.
'soul' is the first definition.
'life force' is the second definition.
(I've seen this in another clue)
(Other definitions for spirit that I've seen before include "Distilled liquor" , "Ghost or soul" , "Eg, rum" , "Gusto" , "Strong distilled alcohol" .)