Back carrying an animal: a dog (6)
I believe the answer is:
basset
'a dog' is the definition.
(basset is a kind of dog)
'back carrying an animal' is the wordplay.
'back' becomes 'bet'.
'carrying' indicates putting letters inside.
'an animal' becomes 'ass' (I've seen this before).
'bet' going around 'ass' is 'BASSET'.
(Other definitions for basset that I've seen before include "Short-legged hound that hunts hares" , "Beasts (anag.)" , "Type of horn" , "GAME" , "Hound (named Fred?)" .)