Increase the rent when you get safely away from (5,3,3)

I believe the answer is:

widen the gap

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'you get safely away from' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'increase the rent' is the wordplay.
'increase' becomes 'widen' (widening is a kind of increasing).
'the rent' becomes 'thegap' (I can't explain this - if you can you should give a lot more credence to this answer).
'widen'+'thegap'='WIDEN THE GAP'

'when' is the link.

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I've seen this clue in the Evening Standard.

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