Zoo heavyweight (5)
I believe the answer is:
rhino
'zoo heavyweight' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rhino that I've seen before include "money in the past" , "In brief, a large horned African animal" , "Horned pachyderm" , "Horned animal; money (slang)" , "Endangered species of large horned herbivore" .)