Puff adder, for instance (5)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
viper
'puff adder for instance' is the definition.
(I know that Bitis arietans is a type of viper)
This is all the clue.
(Other definitions for viper that I've seen before include "Malicious person" , "Malicious type" , "poisonous type" , "Deadly-venomous snake" , "A small poisonous snake" .)