It would bite dad badly with little hesitation (5)
I believe the answer is:
adder
'it would bite' is the definition.
The definition suggests a singular noun which matches the answer.
'dad badly with little hesitation' is the wordplay.
'badly' indicates an anagram (letters in the wrong order).
'with' says to put letters next to each other.
'little hesitation' becomes 'er' (expression of hesitation).
'dad' with letters rearranged gives 'add'.
'add'+'er'='ADDER'
Can you help me to learn more?
(Other definitions for adder that I've seen before include "He's making an extension" , "Mathematical reptile" , "a poisonous type" , "on country walks?" , "An arithmetic snake" .)