Only four-letter Great Lake (4)
I believe the answer is:
erie
'only four-letter great lake' 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 "A Great American lake - sounds spooky" , "One of the Great Lakes" , "The lake sounds weird" , "North american lake sounds spooky" , "Buffalo's lake" .)