Upset Seddon’s eccentricity (7)

I believe the answer is:

oddness

'eccentricity' is the definition.
(oddness is a kind of eccentricity)

'upset seddon's' is the wordplay.
'upset' indicates anagramming the letters.
'seddons' is an anagram of 'ODDNESS'.

(Other definitions for oddness that I've seen before include "Peculiarity characteristic" , "Peculiar quality" , "It isn't even" , "Eccentricity" , "a peculiarity of character" .)

I've seen this clue in the Sydney Morning Herald.

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