The most common and most likely answer to this crossword clue is the 4 letter word KART
K
A
R
T
More clues leading to the result KART
Buddy explains!

The straight part
We know that "Mini car" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mini car = kart.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 KART mean?
KART noun- A go-cart.
- To ride in a go-cart.