Horned mammal (5)
I believe the answer is:
rhino
'horned mammal' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rhino that I've seen before include "Horny creature" , "Hi, Ron! (anag)" , "one might charge in Africa" , "Beastly type that could charge you" , "Hi, Ron, this animal is abbreviated" .)