Red light district's close - a snog with lips can be arranged (4,6)

I believe the answer is:

stop signal

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'close a snog with lips can be arranged' is the definition.
I can't tell whether this defines the answer.

'red light district's' is the wordplay.
'red light' becomes 'stop' (I've seen this in another clue).
'district' becomes 'signal' (I can't explain this - if you can you should give a lot more credence to this answer).
'stop'+'signal'='STOP SIGNAL'

Can you help me to learn more?

I've seen this clue in The Independent.

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