The most common and most likely answer to this crossword clue is the 5 plus 5 letter word FIRST CLASS
I've seen this crossword clue in Financial Times
F
I
R
S
T
C
L
A
S
S
Buddy explains!
The straight part
We know that "form of travel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case form of travel = first class.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 FIRST CLASS mean?
FIRST CLASS noun- (A status, section, etc which is of) premier rank.
- The third year of primary school, following after the junior and senior infant levels.
- One of two classes of city government in the U.S. state of Kentucky, in which cities elect a mayor and aldermen.