Characters upset princess with things (10)

I believe the answer is:

identities

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'characters' is the definition.
The answer and definition can be both human attributes as well as being plural nouns.
Perhaps they are linked in a way I don't understand?

'upset princess with things' is the wordplay.
'upset' says the letters should be written backwards.
'princess' becomes 'di' (Princess Diana).
'with' says to put letters next to each other.
'things' becomes 'entities' (I've seen this in another clue).
'di' in reverse letter order is 'id'.
'id'+'entities'='IDENTITIES'

Can you help me to learn more?

(Other definitions for identities that I've seen before include "Particularities" , "Who people are" .)

I've seen this clue in The Guardian.

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