They can blow the lights out (5)
I believe the answer is:
fuses
'lights out' is the definition.
The answer and definition can be both related to change as well as being verbs in their -s form.
Perhaps there's an association between them I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for fuses that I've seen before include "Blends together as with heat" , "Blow one of these and lose your temper" , "bonds" , "Circuit breakers" , "Blends or amalgamates, say metals" .)