Learner with document showing feature of terrain (8)
I believe the answer is:
landmark
'feature of terrain' is the definition.
(a terrain or landscape has landmarks)
'learner with document' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'with' becomes 'and'.
'document' becomes 'mark' (document can mean to mark or record).
'l'+'and'+'mark'='LANDMARK'
'showing' is the link.
(Other definitions for landmark that I've seen before include "Shard, for example" , "Turning point, watershed" , "Momentous event" , "Significant feature or event" , "cairn, possibly" .)