The laziness of an animal (5)
I believe the answer is:
sloth
I believe this clue is a double definition.
'the laziness' is the first definition.
(sloth is a kind of laziness)
'an animal' is the second definition.
(sloth is a kind of animal)
'of' acts as a link.
(Other definitions for sloth that I've seen before include "Arboreal creature" , "Torpor" , "Aversion to industry" , "Inertia" , "Jungle mammal; laziness" .)