Top dog eviscerated either snake (5)
I believe the answer is:
viper
'snake' is the definition.
(I know that snake can be written as Viper)
'top dog eviscerated either' is the wordplay.
'top dog' becomes 'vip' (I can't justify this - if you can you should give a lot more credence to this answer).
'eviscerated' says to hollow out the word (remove centre letters) (the word is disembowelled of its inside letters).
'either' with its middle removed is 'er'.
'vip'+'er'='VIPER'
Can you help me to learn more?
(Other definitions for viper that I've seen before include "Adder" , "treacherous type" , "spiteful person" , "poisonous type" , "A poisonous snake or treacherous person" .)