The most common and most likely answer to this crossword clue is the 2 plus 5 letter word EN ROUTE
I've seen this crossword clue in The Daily Telegraph
E
N
R
O
U
T
E
More clues leading to the result EN ROUTE
- Ten Euros, not shillings, wasted when travelling
- Starter of cabbage leaves baked in pastry on the way
- Whilst travelling north, hiding amongst Europeans
- Bound for Rouen, perhaps, with a note
- On the way from France?
- On the way to speaking French?
- 10 euro demand on the way
- On the way out, collared by class first off
- Traveller is thus seen limitlessly in northern retreat? Quite the opposite
- It’s baked in pastry, not cold, for during the journey
Buddy explains!

The straight part
We know that "On the way" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case on the way = en route.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.