Pointless showing wit and energy (2,3)
I believe the answer is:
no use
'pointless' is the definition.
(I've seen this before)
'wit and energy' is the wordplay.
'wit' becomes 'nous' (I have seen 'Native wit' mean 'nous' so perhaps 'wit' could also mean 'nous').
'and' is a charade indicator (letters next to each other).
'energy' becomes 'e' (physics symbol as in E=mc2).
'nous'+'e'='NO USE'
'showing' is the link.
(Other definitions for no use that I've seen before include "won't help?" , "Futile" , "Ineffectual" , "Pointless" .)