It could give you something extra poisonous (5)
I believe the answer is:
adder
'it could give you something extra poisonous' is the definition.
The definition suggests a singular noun which matches the answer.
'it' is the wordplay.
I cannot quite see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is located in the answer.
The remaining letters 'addr' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for adder that I've seen before include "Poisonous Brit. snake" , "British snake; summer" , "Sliding" , "Totter" , "He's making an extension" .)