Crossword Genius

Bill as user of letterbox? (6)

Ross

I believe the answer is:

poster

I believe this is a double definition.

'bill' is the first definition.
(I know that bill can be written as poster)

'user of letterbox?' is the second definition.
(someone posting a letter)

'as' acts as a link.

(Other definitions for poster that I've seen before include "Paper advertisement for topers" , "Large printed bill" , "Large decorative printed picture" , "Large advert" , "Large sheet of paper advertising something" .)

I've seen this clue in The Times.
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