Some shaky tremors in the underground, abroad (5)
I believe the answer is:
metro
'some shaky tremors in' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for metro that I've seen before include "French underground" , "what moves many Parisians" , "Paris underground rail system" , "The underground railway system in Paris" , "Parisian underground system" .)