Make journey spanning grand line of high ground (5)
I believe the answer is:
ridge
'high ground' is the definition.
(I've seen this before)
'make journey spanning grand line' is the wordplay.
I cannot really understand how this works, but
'grand' could be 'g' (G is short for grand as in a thousand) and 'g' is found within the answer.
'journey' could be 'ride' (ride is a kind of journey) and 'ride' is present in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'of' is the link.
Can you help me to learn more?
(Other definitions for ridge that I've seen before include "German Baltic port, Buxtehude home" , "Hog's back" , "roof-tree" , "Backbone of a whale" , "Narrow elevated strip" .)