Peripheral route is surveyed top to bottom (5)

I believe the answer is:

outer

I'm a little stuck... Click here to teach me more about this clue!

'peripheral' is the definition.
(I've seen this before)

'route is surveyed top to bottom' is the wordplay.
'route' can be anagrammed to 'OUTER'.
Though, I'm not sure how the anagram is indicated.

Can you help me to learn more?

(Other definitions for outer that I've seen before include "External kind of route" , "External; part of archery target" , "Objective" , "Route (anag.)" , "Poor shot" .)

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

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.