Bottom of the lake is spooky (5)
I believe the answer is:
eerie
'spooky' is the definition.
('eerie' can be a synonym of 'spooky')
'bottom of the lake' is the wordplay.
'bottom of' suggests the final letters.
'lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
The last letter of 'the' is 'e'.
'e'+'erie'='EERIE'
'is' acts as a link.
(Other definitions for eerie that I've seen before include "Spectral" , "Strange and disturbing" , "Bloodcurdling" , "Spooky, weird" , "Spooky, creepy" .)