With no energy at all, somehow become ace at vault (8)
I believe the answer is:
catacomb
'vault' is the definition.
(I have seen 'underground vault' mean 'catacomb' so perhaps 'vault' could also mean 'catacomb')
'with no energy at all somehow become ace' is the wordplay.
I cannot quite understand how this works, but
'no' could be 'o' (O resembles 0) and 'o' is found within the answer.
'energy' could be 'ac' (AC is an example) and 'ac' is located in the answer.
'at' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'at' acts as a link.
(Other definitions for catacomb that I've seen before include "Subterranean cemetery" , "Underground cemetery with recesses for tombs" , "burial site" , "cellar" , "Underground tunnel for bodies" .)