High land coming closer in journey (5)
I believe the answer is:
ridge
'high land' is the definition.
(I've seen this before)
'coming closer in journey' is the wordplay.
'closer' suggests the final letters (the letter which 'closes' the word).
'in' is an insertion indicator.
'journey' becomes 'ride' (ride is a kind of journey).
The last letter of 'coming' is 'g'.
'g' put into 'ride' is 'RIDGE'.
(Other definitions for ridge that I've seen before include "Line where two upward sloping surfaces meet" , "Raised edge" , "Top of roof or incline" , "Highland area" , "Raised strip of land" .)