Authorisation for faulty gas turbine releasing boron (9)

I believe the answer is:

signature

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'authorisation' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

'faulty gas turbine releasing boron' is the wordplay.
'faulty' indicates anagramming the letters.
'releasing' suggests deleting specific letters.
'boron' becomes 'B' (synonyms).
'gas'+'turbine'='gasturbine'
'gasturbine' with 'b' taken out is 'gasturine'.
'gasturine' is an anagram of 'SIGNATURE'.

'for' acts as a link.

Can you help me to learn more?

(Other definitions for signature that I've seen before include "time indicated by this?" , "Identifying piece of writing, tune etc" , "X-WORD ?" , "Mark of individuality" , "Squiggle perhaps" .)

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

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