Current introduced to island's power supplies (5)
I believe the answer is:
mains
'power supplies' is the definition.
Although both the answer and definition are plural nouns, I cannot see how one could define the other.
'current introduced to island's' is the wordplay.
'current' becomes 'I' (symbol for electric current).
'introduced to' indicates putting letters inside.
'island's' becomes 'Man's' (the Isle of Man is an example).
'i' going inside 'mans' is 'MAINS'.
Can you help me to learn more?
(Other definitions for mains that I've seen before include "Distribution network" , "Utility network" , "Followers of those starting" , "Water, gas or electricity supply" , "power supply" .)