New arc light absorbing energy makes you listless (9)
I believe the answer is:
lethargic
'listless' is the definition.
(I've seen this before)
'new arc light absorbing energy' is the wordplay.
'new' indicates anagramming the letters.
'absorbing' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'arc'+'light'='arclight'
'arclight' with letters rearranged gives 'lthargic'.
'lthargic' going around 'e' is 'LETHARGIC'.
'makes you' acts as a link.
(Other definitions for lethargic that I've seen before include "Short of energy" , "Sluggish and apathetic" , "lack of energy" , "Listless" , "without energy" .)