The most common and most likely answer to this crossword clue is the 9 letter word PUBLICITY
I've seen this crossword clue in Financial Times
P
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More clues leading to the result PUBLICITY
Buddy explains!

The straight part
We know that "advertising" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case advertising = publicity.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PUBLICITY mean?
PUBLICITY noun- Advertising or other activity designed to rouse public interest in something.
- Public interest attracted in this way.
- The condition of being the object of public attention.