Verge on being a sort of collie? (6)
I believe the answer is:
'verge' is the definition.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for border that I've seen before include "Line between countries" , "An edgy place" , "Frontier or edge as of garden" , "Rim" , "BLINK/BRINK" .)