Payment demanded for stored electricity? (6)
I believe the answer is:
charge
This clue is a double definition.
'payment demanded' is the first definition.
(charge for a service)
'stored electricity?' is the second definition.
(as in charge in a battery)
'for' acts as a link.
(Other definitions for charge that I've seen before include "Demand price; accuse" , "Control" , "Load - price" , "person in custody" , "Impose fee on" .)