What's unimportant as compared with former currency? (6,3,4)

I believe the answer is:

beside the mark

'what's unimportant' is the definition.
(beside the mark can mean unimportant)

'compared with former currency?' is the wordplay.
'compared with' becomes 'beside' (I've seen this before).
'former currency?' becomes 'themark' (the Mark, former German currency).
'beside'+'themark'='BESIDE THE MARK'

'as' is the link.

I've seen this clue in The Times.

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