The most common and most likely answer to this crossword clue is the 3 plus 2 plus 3 plus 4 letter word PUT IN THE BOOT
I've seen this crossword clue in The Guardian
P
U
T
I
N
T
H
E
B
O
O
T
Buddy explains!
The straight part
We know that "Take a tough line/Take a tough line/deal with a motoring case/deal with a motoring case" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case take a tough line/take a tough line/deal with a motoring case/deal with a motoring case = put in the boot.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.