Don't live as long when holding in vitality (10)
I believe the answer is:
liveliness
'vitality' is the definition.
(thesaurus)
'don't live as long when holding' is the wordplay.
I cannot really see how this works, but
an anagram of 'live' is 'ivel' which is present in the answer.
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
'long' could be 'l' and 'l' is located in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'in' acts as a link.
Can you help me to learn more?
(Other definitions for liveliness that I've seen before include "Energy" , "State of energetic activity" .)