The most common and most likely answer to this crossword clue is the 6 plus 5 letter word NUMBER PLATE
I've seen this crossword clue in The Guardian
N
U
M
B
E
R
P
L
A
T
E
More clues leading to the result NUMBER PLATE
Buddy explains!

The straight part
We know that "vehicle identification" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vehicle identification = number plate.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.