Narrow, nothing less (4)

I believe the answer is:

thin

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'narrow' is the definition.
(similar in meaning)

'nothing less' is the wordplay.
'THIN' is hidden in amongst the letters.
However, I am unsure how this is indicated.

Can you help me to learn more?

(Other definitions for thin that I've seen before include "as 7 [LOAF] may be sliced" , "(Of smile) weak, forced" , "Lean; make (plants) less crowded" , "Carrying little fat" , "Slim - watery" .)

I've seen this clue in the Evening Standard.

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