Large mammal, for short (5)
I believe the answer is:
hippo
'large mammal for short' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hippo that I've seen before include "Massive thick-skinned animal of African rivers" , "Tropical African mud wallower" , "one that's large and fleshy" , "Aquatic mammal" , "Thick-skinned type" .)