The most common and most likely answer to this crossword clue is the 5 plus 7 letter word PARTS COMPANY
I've seen this crossword clue in The Daily Telegraph
P
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S
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More clues leading to the result PARTS COMPANY
Buddy explains!
The straight part
We know that "Splits up/firm producing vehicle components" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case splits up/firm producing vehicle components = parts company.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.