Perimeter route maybe (5)

I believe the answer is:

outer

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'perimeter route maybe' is the definition.
I can't tell whether this definition defines the answer.

'route maybe' is the wordplay.
'maybe' is an anagram indicator.
'route' anagrammed gives 'OUTER'.

Can you help me to learn more?

(Other definitions for outer that I've seen before include "Surrounding" , "Objective" , "Ring for double scores on a dartboard" , "External; part of archery target" , "On the periphery" .)

I've seen this clue in the Evening Standard.

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