Whimsically, a light switch is for sale (2,5)
I believe the answer is:
on offer
'whimsically' is the definition.
I know nothing about this answer so I cannot tell whether this works.
'a light switch is for sale' is the wordplay.
I cannot quite understand how this works, but
'switch' could be 'off' (I've seen this in another clue) and 'off' is present in the answer.
'a' could be 'one' and 'one' is found within the leftover letters.
A single letter 'r' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for on offer that I've seen before include "At special price" , "is made cheaper?" , "For sale at specified price" , "For sale at a certain price" , "available for less" .)