Where the outer lid is different from the inner lid? (6)
I believe the answer is:
hatbox
'where the outer lid is different from the inner' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'lid?' is the wordplay.
I cannot quite see how this works, but
'lid?' could be 'hat' ('hat' can be a synonym of 'lid') and 'hat' is present in the answer.
The remaining letters 'box' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hatbox that I've seen before include "Container for headwear" , "Ten-gallon container maybe" , "Case for storing headgear" , "Milliner's container" , "Headgear container" .)