Setter one definite nit, among others (7)

I believe the answer is:

measure

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'nit among others' is the definition.
I can't tell whether this definition defines the answer.

'setter one definite' is the wordplay.
'setter' becomes 'me' (the setter of the clue).
'one' becomes 'a' (a thing is one thing).
'definite' becomes 'sure' (synonyms).
'me'+'a'+'sure'='MEASURE'

Can you help me to learn more?

(Other definitions for measure that I've seen before include "Gauge" , "Ascertain dimensions" , "Tape" , "Calculate size" , "Extent" .)

I've seen this clue in The Independent.

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