Not the inner route construction (5)

I believe the answer is:

outer

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

'route construction' is the wordplay.
'construction' indicates an anagram (answer constructed from certain letters).
'route' anagrammed gives 'OUTER'.

Can you help me to learn more?

(Other definitions for outer that I've seen before include "External; part of archery target" , "External; peripheral" , "Objective" , "Archer's shot" , "Outside; external" .)

I've seen this clue in The Globe and Mail.

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