International organisation hasn't tried uncertified transport (6)

I believe the answer is:

unicef

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'international organisation' is the definition.
'UNICEF' can be an answer for 'organisation' (UNICEF is an example). I am unsure of the 'international' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for unicef that I've seen before include "Organisation for helping children and mothers in developing countries" , "international agency" , "UN organisation responsible for aid to children" , "UN children's organisation" , "International organisation for education of children in developing countries" .)

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

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