International line? (6)
I believe the answer is:
border
This might be a double definition.
'international' is the first definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'line?' is the second definition.
(border is a kind of line)
Can you help me to learn more?
(Other definitions for border that I've seen before include "Frontier or edge as of garden" , "Boundary line" , "Bound" , "Line between countries" , "An edgy place" .)