Lethal vanilla included sweet (5)
I believe the answer is:
halva
'sweet' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'lethal vanilla included' is the wordplay.
'included' indicates a hidden word (I've seen 'includes' mean this).
'HALVA' is hidden within 'lethal vanilla'.
Can you help me to learn more?
(Other definitions for halva that I've seen before include "Sweetmeat, originally Turkish, with sesame seeds and honey" , "Sesame flour and honey confection" , "Indian sweetmeat with honey and nuts" , "Mediterranean sweetmeat" , "Honeyed sweetmeat" .)