Great but creepy sounding lake (4)
I believe the answer is:
erie
'great but creepy sounding lake' is the definition.
'erie' can be an answer for 'lake' (Lake Erie is one of the Canadian/US 'Great Lakes'). I'm not sure about the 'great but creepy sounding' bit.
'sounding lake' is the wordplay.
'sounding' indicates a 'sounds like' (homophone) clue.
'lake' becomes 'eerie'.
'eerie' sounds like 'ERIE'.
Can you help me to learn more?
(Other definitions for erie that I've seen before include "Lake between Canada and the US" , "Superior companion" , "North american lake sounds spooky" , "Great lake in Eire" , "Buffalo's lake" .)