Specific number for a county division (7)

I believe the answer is:

hundred

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This could be a double definition.

'specific number' is the first definition.
'hundred' can be an answer for 'number' (hundred is a kind of whole number). I'm not sure about the 'specific' bit.

'county division' is the second definition.
(I've seen this before)

'for a' is the link.

Can you help me to learn more?

(Other definitions for hundred that I've seen before include "Century" , "Old division of a county" , "entirely associated with 27 [PERCENT]" , "cricketing achievement" , "number of scores" .)

I've seen this clue in The Irish News.

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