Cleopatra biter (3)
I believe the answer is:
asp
'cleopatra biter' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for asp that I've seen before include "Snake of the Nile" , "It proved deadly for Cleopatra" , "Snake found in spa" , "Slithery thing" , "A glider's what's called for" .)