The most common and most likely answer to this crossword clue is the 13 letter word UNDERCARRIAGE
I've seen this crossword clue in The Daily Telegraph
U
N
D
E
R
C
A
R
R
I
A
G
E
More clues leading to the result UNDERCARRIAGE
- Less than the cost of transporting part of plane?
- Changed gear, ruined car, or part of one
- Apparatus for landing gear in a cruder alternative
- Part of plane to develop during a career
- Engineer reducing a rear part of plane
- Part of aircraft that is in transportation, apparently
- Part of car transport cost after European articles
Buddy explains!

The straight part
We know that "Part of car" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part of car = undercarriage.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 UNDERCARRIAGE mean?
UNDERCARRIAGE noun- The supporting structural framework of a vehicle.
- The landing gear of an aircraft.
- The genitalia.