Harsh to cut off electricity at first (6)
I believe the answer is:
severe
'harsh' is the definition.
(I've seen this before)
'cut off electricity at first' is the wordplay.
'cut off' becomes 'sever' (to sever is to cut).
'at first' indicates taking the first letters.
The initial letter of 'electricity' is 'e'.
'sever'+'e'='SEVERE'
'to' is the link.
(Other definitions for severe that I've seen before include "Austere, serious" , "Harsh and stringent" , "Forbidding in action or appearance" , "Acute" , "Sharp" .)