Quietly evasive royal intern is everywhere (9)

I believe the answer is:

pervasive

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'quietly evasive royal' is the definition.
Both the answer and definition are adjectives. Maybe you can see a link between them that I can't see?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for pervasive that I've seen before include "Widely-spread" , "Spreading throughout" , "Widespread" .)

I've seen this clue in the Sydney Morning Herald.

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