Be a squatter with determination? (3,2,9)

I believe the answer is:

sit in judgement

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'be' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's a link between them I don't understand?

'a squatter with determination?' is the wordplay.
'a squatter with' becomes 'sitin' (I can't justify this - if you can you should give a lot more credence to this answer).
'determination?' becomes 'judgement' (determination is a kind of judgement).
'sitin'+'judgement'='SIT IN JUDGEMENT'

Can you help me to learn more?

I've seen this clue in The Guardian.

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