Large, short-haired dog (7)
I believe the answer is:
mastiff
'large short-haired dog' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mastiff that I've seen before include "Hound" , "Large short-haired dog breed" , "Strong breed of dog" , "Powerful dog breed" , "Large, powerful, short-haired dog" .)