Spookily strange (5)
I believe the answer is:
eerie
'spookily strange' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eerie that I've seen before include "Strangely frightening" , "Strange and disturbing" , "Uncannily strange" , "Unnerving" , "Spooky, creepy" .)