Canton bordering the Lake of Lucerne (3)
I believe the answer is:
uri
'canton bordering the lake of lucerne' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for uri that I've seen before include "___ Geller, Israeli spoon-bender" , "- - Geller (celebrity)" , "--- Geller; Swiss canton" .)