Don't part with remaining traffic sign (4,4)

I believe the answer is:

keep left

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'remaining traffic sign' is the definition.
I know nothing about this answer so I can't tell whether this works.

'don't part' is the wordplay.
'don't' becomes 'keep' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'part' becomes 'left' (left is a kind of part).
'keep'+'left'='KEEP LEFT'

'with' is the link.

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