Characteristic of monorail enthusiast? (3-5,4)
I believe the answer is:
one-track mind
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for one-track mind that I've seen before include "Very basic obsession?" , "Brain preoccupied with a single subject" , "Obsession with a single objective" , "A very limited thinker?" , "Obsessive attitude to a subject" .)
