Tax fetters John: fortune needed for building land (6,3)

I believe the answer is:

vacant lot

I'm a little stuck... Click here to teach me more about this clue!

'building land' is the definition.
The answer and definition can be both locations as well as being singular nouns.
Maybe you can see an association between them that I don't see?

'tax fetters john fortune' is the wordplay.
I cannot quite understand how this works, but
'john' could be 'can' (both can informally mean toilet) and 'can' is present in the answer.
'tax' could be 'vat' (British sales tax) and 'vat' is located in the leftover letters.
'fortune' could be 'lot' (as in a person's lot in life) and 'lot' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'needed for' is the link.

Can you help me to learn more?

I've seen this clue in The Independent.

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