Brusque dismissal when uncle’s out of credit (5)

I believe the answer is:

scram

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'brusque dismissal when' is the definition.
I can't judge whether this defines the answer.

'uncle's out of credit' is the wordplay.
'uncle' becomes 'sam' (Uncle Sam is an example).
'out of' indicates putting letters inside.
'credit' becomes 'cr'.
'sam' placed around 'cr' is 'SCRAM'.

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(Other definitions for scram that I've seen before include "make emergency shut-down" , "Shoo!" , "Leave quickly" , "Skedaddle!" , "Scarper" .)

I've seen this clue in the Evening Standard.

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