Built-up area of urban development (4,4)

I believe the answer is:

hill town

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'urban development' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'built-up area' is the wordplay.
'built-up' becomes 'hill' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'area' becomes 'town' (town is a kind of area).
'hill'+'town'='HILL TOWN'

'of' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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