Need it if in trouble or not sure (10)

I believe the answer is:

indefinite

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'not sure' is the definition.
I can't tell whether this defines the answer.

'need it if in trouble' is the wordplay.
'trouble' is an anagram indicator.
'need'+'it'+'if'+'in'='needitifin'
'needitifin' anagrammed gives 'INDEFINITE'.

'or' is the link.

Can you help me to learn more?

(Other definitions for indefinite that I've seen before include "Vague" , "Loose" , "rough" , "Not decided or not known" , "Like a" .)

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

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