Clue: Matthew, for one, got all flustered on the Paris commuter service (12)
Answer: TOLL-GATHERER
Explanation: Definition: Matthew, for one
(GOT ALL)* + THE + RER (the Parisian railway network Réseau Express Régional – as the rubric says, this abbreviation is not in Chambers. The disciple Matthew is described as a "publican", meaning a tax-gatherer