French here penning in rebellious Brits (5)

I believe the answer is:

iceni

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'rebellious brits' is the definition.
(the Iceni were an Iron Age tribe of Britain)

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

Can you help me to learn more?

(Other definitions for iceni that I've seen before include "Old tribe" , "Ancient tribesmen" , "Ancient British tribe" , "people rebelling against Rome" , "British people once" .)

I've seen this clue in The Times.

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