Left it switched on? (3)
I believe the answer is:
lit
'switched on?' is the definition.
The answer and definition can be both related to change as well as being past participle verbs.
Perhaps there's a link between them I don't understand?
'left it' is the wordplay.
'left' becomes 'l' (common abbreviation).
'l'+'it'='LIT'
Can you help me to learn more?
(Other definitions for lit that I've seen before include "Enlightened" , "Creative writing, in short" , "was illuminating" , "Set alight" , "Fired" .)