Inadvertent publicity? (6)

I believe the answer is:

advert

I'm a little stuck... Click here to teach me more about this clue!

'publicity?' is the definition.
(advert is a kind of publicity)

'inadvertent' is the wordplay.
'ADVERT' is hidden in amongst the letters.
But, I'm uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for advert that I've seen before include "Public notice" , "piece of publicity" , "Notice promoting goods" , "Plug (abbr)" , "Refer or allude" .)

I've seen this clue in the Evening Standard.

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