We ponder treatment that's not new (3-5)

I believe the answer is:

pre-owned

'not new' is the definition.
(I've seen this in another clue)

'we ponder treatment' is the wordplay.
'treatment' is an anagram indicator (letters treated or processed differently).
'we'+'ponder'='weponder'
'weponder' is an anagram of 'PRE-OWNED'.

'that's' acts as a link.

(Another definition for pre-owned that I've seen is " Used".)

I've seen this clue in The Irish Times.

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