Something outstanding as rarer perhaps (7)

I believe the answer is:

arrears

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'something outstanding' is the definition.
I can't tell whether this defines the answer.

'as rarer perhaps' is the wordplay.
'perhaps' indicates an anagram.
'as'+'rarer'='asrarer'
'asrarer' is an anagram of 'ARREARS'.

Can you help me to learn more?

(Other definitions for arrears that I've seen before include "If in these, the money is overdue" , "In these, one is behind with payments" , "They're outstanding" , "Outstanding payments" , "Ourtstanding payments" .)

I've seen this clue in The Sun.

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