Crossword Genius

A sign that visitors aren't welcome (2,5)

Ross

There are a few possibilities for this:

Which length description are you looking for?:

2,5

2,8

4,3
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'visitors aren't welcome' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'a sign' is the wordplay.
I cannot really understand how this works, but
'a' could be 'an' and 'an' is found in the answer.
This explanation may well be incorrect...

'that' is the link.

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I've seen this clue in The Globe and Mail.
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