One to ignore grandma has struck arrogant pose outside (7,3,5)
I believe the answer is:
persona non grata
'one' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'ignore grandma has struck arrogant pose outside' is the wordplay.
I cannot quite see how this works, but
'grandma' could be 'nan' (I've seen this before) and 'nan' is found within the answer.
This explanation may well be incorrect...
'to' is the link.
Can you help me to learn more?
(Other definitions for persona non grata that I've seen before include "One banned" , "Undesirable" .)