Crossword Genius

In our array, there's nothing even or odd for Napier (4)

Ross

I believe the answer is:

orra

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'in our array there's nothing even' is the definition.
I know nothing about this answer so I can't tell whether this works.

'or odd for napier' is the wordplay.
'odd for napier' becomes 'ra' (I can't explain this - if you can you should give a lot more credence to this answer).
'or'+'ra'='ORRA'

Can you help me to learn more?

(Other definitions for orra that I've seen before include "Scotch left over" , "unmatched in Scotland" , "Occasional Scotch" .)

I've seen this clue in The Telegraph.
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