What’s left after touching electricity supply? (7)
I believe the answer is:
remains
'what's left' is the definition.
(what remains or is left behind)
'after touching electricity supply?' is the wordplay.
'after' is a charade indicator (letters next to each other).
'touching' becomes 're' (both can mean concerning or relating to).
'electricity supply?' becomes 'mains' (I've seen this before).
're' next to 'mains' is 'REMAINS'.
(Other definitions for remains that I've seen before include "dead body the result?" , "Stays; dead body" , "Corpse; relics" , "Body after death" , "Historical relics" .)