The most common and most likely answer to this crossword clue is the 7 letter word CARSICK
I've seen this crossword clue in The Times
C
A
R
S
I
C
K
Buddy explains!

The straight part
We know that "green motoring" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case green motoring = carsick.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CARSICK mean?
CARSICK adjective- Dizzy or feeling nauseated due to riding in a vehicle; suffering from motion sickness.