Hooded serpent (5)
I believe the answer is:
cobra
'hooded serpent' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cobra that I've seen before include "hamadryad" , "Reptile (found in Cabinet Office Briefing Room A?)" , "Sinuous creature" , "Poisoner" , "Something with a hood" .)