One's paid to kill two animals at home (8)
I believe the answer is:
assassin
'one's paid to kill' is the definition.
(a paid killer)
'two animals at home' is the wordplay.
'two animals' can mean two substitutions for 'animal'.
'animal' becomes 'ass' (term for a donkey).
'animal' becomes 'ass' (term for a donkey).
'at home' becomes 'in' (similar in meaning).
'ass'+'ass'+'in'='ASSASSIN'
(Other definitions for assassin that I've seen before include "Liquidator" , "Political murderer" , "Murderer (of prominent figure)" , "I kill" , "Hired murderer" .)