Passed a range we know south of plain (9)
I believe the answer is:
overtaken
'passed' is the definition.
('overtake' can be a synonym of 'pass')
'a range we know south of plain' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
'range' could be 'ken' (ken can mean someone's range of knowledge) and 'ken' is found in the answer.
'of' could be 'o' and 'o' is located in the answer.
The remaining letters 'vert' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for overtaken that I've seen before include "left behind" , "Passed on road" .)