Fagin's associate gets on in advertising (10)

I believe the answer is:

billboards

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'fagin's associate gets on in advertising' is the definition.
I can't judge whether this defines the answer.

'fagin's associate gets on' is the wordplay.
'fagin's associate' becomes 'bill' (I am not sure about this - if you are sure you should believe this answer much more).
'gets on' becomes 'boards' ('board' can be a synonym of 'get on').
'bill'+'boards'='BILLBOARDS'

Can you help me to learn more?

(Another definition for billboards that I've seen is " More than one hoarding".)

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