Niagara's source (4)

I believe the answer is:
erie
'niagara's source' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for erie that I've seen before include "N. American lake" , "Superior companion" , "North american lake sounds spooky" , "Lake between Canada and the US" , "Buffalo's lake" .)