Source of power wasted in loading train (8,4)
I believe the answer is:
national grid
'source of power wasted' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'loading train' is the wordplay.
'loading train' can be anagrammed to 'NATIONAL GRID'.
However, I am not sure how this is indicated.
'in' is the link.
Can you help me to learn more?
(Other definitions for national grid that I've seen before include "Power distribution network" , "plenty of power here" , "High-voltage distribution system" , "Supplier of current" , "Geographical coordinate system used in UK" .)