A sign that visitors aren't welcome (2,8)
(Other definitions for no entry that I've seen before include "street sign" , "Admittance prohibited!" .)
'welcome' is the definition.
Although both the answer and definition are verbs in their base form, I cannot see how one could define the other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for keep out that I've seen before include "warning note to trespassers?" , "sign of an exclusive establishment" , "No entry!" , "notice to trespassers?" , "Don't trespass" .)
'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.
Can you help me to learn more?