Possible Clues:

• Move to another place a problem for rail passengers? Not I
• Express (words) in another language
• In other words, the trains without one are behind time
• Change coaches but with one leaving behind schedule
• Decode, in a way
• Evidence of railway delays one is wanting to make comprehensible
• Change to another language
• Make understandable
• Decipher what's left after leaving harbour in 6 down after hours
• Tutor not one to criticise convert