An element of impertinence (3)

I believe the answer is:

tin

'an element' is the definition.
(tin is a kind of element)

'of impertinence' is the wordplay.
'of' says the answer is hidden in the clue.
'TIN' can be found hidden inside 'impertinence'.

(Other definitions for tin that I've seen before include "Money" , "A silvery-white metal often in cans" , "loaf of bread" , "Atomic number 50" , "1 down, symbol Sn" .)

I've seen this clue in the Evening Standard.

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