Lowly worker mostly impudent when turning up (4)

I believe the answer is:

serf

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'lowly worker' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for serf that I've seen before include "Feudal labourer" , "Feudal estate worker" , "who got into bondage" , "Slave" , "Peasant, agricultural labourer" .)

I've seen this clue in The Times.

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