Person who invents revolutionary form of transport (4)
I believe the answer is:
rail
'form of transport' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rail that I've seen before include "Complain bitterly - wading bird" , "Bar - marsh bird" , "Kind of transport" , "Rant" , "Bar of track or fence" .)