Drunken topers four to a bed? (6)

I believe the answer is:

poster

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

'four to a bed?' is the definition.
I can't tell whether this defines the answer.

'drunken topers' is the wordplay.
'drunken' indicates anagramming the letters.
'topers' with letters rearranged gives 'POSTER'.

Can you help me to learn more?

(Other definitions for poster that I've seen before include "Large advertisement" , "Large sheet of paper advertising something" , "Bill or placard" , "'Notice, placard (6)'" , "Paper advertisement for topers" .)

I've seen this clue in the Evening Standard.

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