Narrow elevation head of geography observed during journey (5)
I believe the answer is:
ridge
'narrow elevation' is the definition.
(I've seen this in another clue)
'head of geography observed during journey' is the wordplay.
'head of' indicates taking the first letters.
'observed during' indicates putting letters inside.
'journey' becomes 'ride' (ride is a kind of journey).
The initial letter of 'geography' is 'g'.
'g' inserted within 'ride' is 'RIDGE'.
(Other definitions for ridge that I've seen before include "Line of higher ground" , "Long narrow crest" , "Long raised band" , "Part of mountain" , "Raised edge" .)