Pay no attention to separatist with no attire (4)

I believe the answer is:

pass

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'pay no' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for pass that I've seen before include "while away" , "exam grade ..." , "good performance by exam candidate" , "What a hooker may do" , "Don't answer a question" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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