Some cobra venom in bird (5)
I believe the answer is:
raven
'bird' is the definition.
(raven is a kind of bird)
'some cobra venom in' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'RAVEN' is hidden within 'cobra venom in'.
(Other definitions for raven that I've seen before include "flesh-eating bird" , "Flier" , "Large black bird" , "Jet-black" , "Tower of London bird" .)