Walker's not been in such an area (9)
I believe the answer is:
untrodden
'walker's not been in such an area' is the definition.
I can't judge whether this definition defines the answer.
'not been in such an area' is the wordplay.
'not' becomes 'un' (prefix meaning 'not').
'been in such' becomes 'trod' (I can't explain this - if you can you should give a lot more credence to this answer).
'an area' becomes 'den' (den is a kind of area).
'un'+'trod'+'den'='UNTRODDEN'
Can you help me to learn more?
(Other definitions for untrodden that I've seen before include "Description of virgin territory" , "Not having been walked on" , "Unfrequented" .)