Nobleman's six second calculation (8)

I believe the answer is:

viscount

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'nobleman's' is the definition.
(viscount is a kind of nobleman)

'six second calculation' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'second' becomes 's' (common abbreviation).
'calculation' becomes 'count' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'vi'+'s'+'count'='VISCOUNT'

Can you help me to learn more?

(Other definitions for viscount that I've seen before include "British peer" , "plane" , "Lord" , "Minor peer" , "British noble" .)

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

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