One new item's breaking in last minute (13)

I believe the answer is:

infinitesimal

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'one' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?

'new item's breaking in last minute' is the wordplay.
'new' indicates an anagram.
'breaking' is an insertion indicator.
'last minute' becomes 'finial' (I am not sure about this - if you are sure you should believe this answer much more).
'items' is an anagram of 'tesim'.
'in'+'finial'='infinial'
'tesim' placed within 'infinial' is 'INFINITESIMAL'.

Can you help me to learn more?

(Other definitions for infinitesimal that I've seen before include "So small as to be barely discernible" , "Tiny" , "Minuscule" , "Minute" , "Immeasurably small" .)

I've seen this clue in The Telegraph.

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