Vitality, energy (5)
I believe the answer is:
oomph
I believe this is a double definition.
'vitality' is the first definition.
(I've seen this in another clue)
'energy' is the second definition.
(oomph can mean energy or excitement)
(Other definitions for oomph that I've seen before include "Shows excitement aplenty" , "Informal energy or enthusiasm, usually in a girl" , "Enthusiasm - vigour - sex appeal" , "15 [SEXINESS]" , "drive" .)