Journey round grand escarpment (5)
I believe the answer is:
ridge
'escarpment' is the definition.
(I've seen this before)
'journey round grand' is the wordplay.
'journey' becomes 'ride' (ride is a kind of journey).
'round' is an insertion indicator.
'grand' becomes 'G' (G is short for ground as in a thousand).
'ride' placed around 'g' is 'RIDGE'.
(Other definitions for ridge that I've seen before include "Narrow elevated strip" , "Raised edge" , "Raised earth between furrows" , "Hog's-back" , "Long, narrow range of hills" .)