Half a ditch protects long animal (5)
I believe the answer is:
hyena
'animal' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for hyena that I've seen before include "One laughs loud" , "Carnivorous mammal" , "Predatory dog-like animal, makes sound like laughing" , "Laughing carnivore" , "one to laugh" .)