Mirrored number twelve (4)
I believe the answer is:
noon
'twelve' is the definition.
(I've seen this before)
'mirrored number' is the wordplay.
'mirrored' becomes 'noo' (I can't justify this - if you can you should believe this answer much more).
'number' becomes 'n' (n can represent any number).
'noo'+'n'='NOON'
Can you help me to learn more?
(Other definitions for noon that I've seen before include "The middle of the day" , "12 pm" , "when PM starts" , "Twelve during daylight" , "See 8" .)