One abroad investigated without any restraints (9)

I believe the answer is:

unchecked

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'investigated without any restraints' is the definition.
I can't judge whether this definition defines the answer.

'one abroad' is the wordplay.
'one' becomes 'un' (northern English dialect form of 'one').
'abroad' becomes 'checked' (I can't justify this - if you can you should give a lot more credence to this answer).
'un'+'checked'='UNCHECKED'

Can you help me to learn more?

(Other definitions for unchecked that I've seen before include "Flapping about" , "free" .)

I've seen this clue in The Independent.

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