Starter of Chinese leaves in pastry whilst travelling (2,5)

I believe the answer is:

en route

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'travelling' is the definition.
('en route' means on the way)

I cannot understand how the rest of the clue works.

(Other definitions for en route that I've seen before include "While travelling" , "'On the way (2,5)'" , "On the way - in France" , "As part of a journey" , "March" .)

I've seen this clue in The Times.

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