Dad leaves hitchhiker, say, on Middle East express (9)

I believe the answer is:

messenger

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'express' is the definition.
(thesaurus)

I can't explain the remainder of the clue.

(Other definitions for messenger that I've seen before include "He brings the news - don't shoot him" , "One who bears a communication" , "Courier - don't shoot him" , "Emissary, courier" , "The role of Hermes or Mercury?" .)

I've seen this clue in The Independent.

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