Informer, train dispatcher? (7-6)
I believe the answer is:
whistle-blower
'informer' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for whistle-blower that I've seen before include "One who exposes wrongdoing" , "Public-spirited informer" , "One who informs on malpractice" , "Person revealing improper activities" , "Informer on illicit activities" .)