Source of electricity not new in providing illumination (8)
I believe the answer is:
lighting
'not new in providing illumination' is the definition.
'lighting' can be an answer for 'illumination' (lighting is a kind of illumination). I am not sure about the 'not new in providing' bit.
'source of electricity' is the wordplay.
'source' becomes 'light' (I have seen 'Source of illumination ' mean 'light' so perhaps 'source' could also mean 'light').
'of electricity' becomes 'ing' (I can't justify this - if you can you should believe this answer much more).
'light'+'ing'='LIGHTING'
Can you help me to learn more?
(Other definitions for lighting that I've seen before include "landing" , "See 14" , "Visual aids" , "Illumination" , "Starting a fire" .)