Arrange one length to make it easy (7)

I believe the answer is:

lighten

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'make it easy' is the definition.
I can't tell whether this defines the answer.

'arrange one length' is the wordplay.
'arrange' is an anagram indicator.
'one' becomes 'i' (Roman numeral).
'i'+'length'='ilength'
'ilength' is an anagram of 'LIGHTEN'.

'to' acts as a link.

Can you help me to learn more?

(Other definitions for lighten that I've seen before include "Thin leg (anag.)" , "make fairer" , "Make paler" , "Make less burdensome" , "Become brighter" .)

I've seen this clue in the Sydney Morning Herald.

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