Technocrat so rued holding back international transport service (8)
I believe the answer is:
eurostar
'international transport service' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'technocrat so rued holding back' is the wordplay.
'holding' indicates the answer is hidden within the clue.
'back' says the letters should be written backwards.
'ratsorue' is hidden in the letters of 'technocrat so rued'.
'ratsorue' written backwards gives 'EUROSTAR'.
Can you help me to learn more?
(Other definitions for eurostar that I've seen before include "Passenger rail service from London to Paris, etc" , "International train" , "cross-Channel express" , "High-speed rail link between the UK and France" , "Chunnel service" .)