Blair, the writer, has Independent line for right source of energy (3,4)
I believe the answer is:
oil well
'source of energy' is the definition.
'oil well' can be an answer for 'source' (I have seen 'Source of fuel' mean 'oil well' so perhaps 'source' could also mean 'oil well'). I'm unsure of the 'of energy' bit.
'blair the writer has independent line for right' is the wordplay.
I cannot really see how this works, but
'writer' could be 'i' (the person who is writing these clues) and 'i' is found within the answer.
'independent' could be 'we' (the puzzle setter and their Independent colleagues) and 'we' is located in the answer.
'line' could be 'l' (used when specifying particular lines from a poem) and 'l' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for oil well that I've seen before include "Source of black gold" , "Shaft beneath a nodding donkey?" , "Boring - source of petroleum" , "crude container" , "Maintenance advice for metal hinges" .)