A fifty-fifty arrangement for everyone (3)

I believe the answer is:

all

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'everyone' is the definition.
(all people)

'a fifty-fifty' is the wordplay.
'fifty-fifty' becomes 'LL' (L is 50 in Roman numerals).
'a'+'ll'='ALL'

'arrangement for' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?

(Other definitions for all that I've seen before include "SECOND PART OF 8" , "Total" , "None excluded" , "that's as many as there are" , "without exception" .)

I've seen this clue in The Globe and Mail.

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