Crossword Genius

Geographer in vehicle on a high rocky hill (8)

Ross

I believe the answer is:

mercator

I'm a little stuck... Click here to teach me more about this clue!

'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" .)

I've seen this clue in The Telegraph.
Want a hint initially instead of a full solution? Install my app