Be stunned regarding US city railroad (4)
I believe the answer is:
reel
'be stunned' is the definition.
(I've seen this in another clue)
'regarding us city railroad' is the wordplay.
I cannot quite understand how this works, but
'regarding' could be 're' (re can mean regarding, concerning) and 're' is found within the answer.
'railroad' could be 'el' (el is a kind of railroad) and 'el' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for reel that I've seen before include "Folk dance" , "energetic dance" , "Turn around in the dance" , "Part of a film; stagger" , "Show astonishment" .)