One's method of getting over a hill is to drive! (5)
I believe the answer is:
motor
'is to drive' is the definition.
(I've seen this before)
'one's method of getting over a hill' is the wordplay.
'one's method' becomes 'm' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'of' becomes 'o''.
'getting over' means one lot of letters go next to another (in a down clue, some letters go above others).
'a hill' becomes 'tor' (tor is a kind of hill).
'm'+'o'+'tor'='MOTOR'
Can you help me to learn more?
(Other definitions for motor that I've seen before include "Car - car's engine" , "Internal combustion engine" , "Car; travel quickly" , "Car (informal)" , "Move quickly" .)