Geographer in vehicle on a high rocky hill (8)
I believe the answer is:
mercator
'geographer' is the definition.
(I've seen this before)
'in vehicle on a high rocky hill' is the wordplay.
'in vehicle' becomes 'merc' (I can't justify this - if you can you should believe this answer much more).
'on' means one lot of letters go next to another.
'high rocky hill' becomes 'tor' (I've seen this before).
'merc'+'a'+'tor'='MERCATOR'
Can you help me to learn more?
(Other definitions for mercator that I've seen before include "was famous for projection" , "Deviser of projection" , "Flemish geographer and cartographer" , "Flemish mapmaker, giving name to a projection" , "Projectionist" .)