Causing the heebie-jeebies (5)
I believe the answer is:
eerie
'causing the heebie-jeebies' 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 "Weird, uncanny" , "Strangely frightening" , "Weird and disturbing" , "Strange, unusual" , "Frighteningly odd" .)