Turn on or off, then reverse to find railway
I believe the answer is:
switchback
'railway' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for switchback that I've seen before include "uneven way" , "big dipper" , "roller coaster" , "Up-and-down road" , "fair railway system" .)