Enthusiasm; liveliness (5)
I believe the answer is:
verve
This clue is a double definition.
'enthusiasm' is the first definition.
(I've seen this in another clue)
'liveliness' is the second definition.
(I know that verve is a type of energy)
(Other definitions for verve that I've seen before include "Animation" , "Zest and exuberance" , "Dashing enthusiasm" , "Great liveliness or enthusiasm" , "Sparkle" .)