Where to learn how to get out of a car? (6)

I believe the answer is:
harrow
'where to learn how' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'get out of a car?' is the wordplay.
'get' becomes 'how' (I can't justify this - if you can you should give a lot more credence to this answer).
'out of' means one lot of letters goes inside another (some letters on the outside of others).
'car?' becomes 'RR' (Rolls Royce).
'a'+'rr'='arr'
'how' placed around 'arr' is 'HARROW'.
'to' is the link.
Can you help me to learn more?
(Other definitions for harrow that I've seen before include "Soil-breaker; school" , "Soil-breaking implement" , "Plough, school" , "Break up (ground) - distress (feelings)" , "worry" .)
