Peak in clear — one near borders (8)
I believe the answer is:
'peak' is the definition.
'in clear one near borders' is the wordplay.
'in clear' becomes 'rid' ('rid' can be a synonym of 'clear'. I am not sure about the 'in' bit.**).
'one' becomes 'i' (Roman numeral).
'near' becomes 'mean' (I've seen this before).
'borders' indicates putting letters inside.
'ridi' placed into 'mean' is 'MERIDIAN'.
Can you help me to learn more?
(Other definitions for meridian that I've seen before include "Imaginary great circle through North and South poles" , "Peak" , "Circle of longitude" , "Admire in great semi-circle on globe" , "Imaginary great circle on the earth passing through both poles" .)