Traffic impedance into which cork goes (10)
I believe the answer is:
bottleneck
'traffic impedance into which cork goes' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for bottleneck that I've seen before include "Where one may get trapped" , "Constricted place" , "Constricted section of road" , "Congestion" , "Traffic constriction" .)