Spooky European lake (5)
I believe the answer is:
eerie
'spooky' is the definition.
(synonyms)
'european lake' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
'e'+'erie'='EERIE'
(Other definitions for eerie that I've seen before include "Awesome" , "Sinister" , "Weird and disturbing" , "Frighteningly odd" , "Bloodcurdling" .)