Mum has eaten horrible animal (7)
I believe the answer is:
manatee
'animal' is the definition.
The answer is an example.
'mum has eaten horrible' is the wordplay.
'mum' becomes 'ma' (both can mean mother).
'has' is a charade indicator (letters next to each other).
'horrible' is an anagram indicator.
'eaten' with letters rearranged gives 'natee'.
'ma'+'natee'='MANATEE'
(Other definitions for manatee that I've seen before include "Large aquatic mammal -- sea cow" , "Sea denizen" , "'Amen, tea for the aquatic mammal (7)'" , "Beast" , "To find sea cow" .)