Old woman with unyielding dog (7)
I believe the answer is:
mastiff
'dog' is the definition.
(breed of dog)
'old woman with unyielding' is the wordplay.
'old woman' becomes 'ma' (both can mean someone's mother).
'with' is a charade indicator (letters next to each other).
'unyielding' becomes 'stiff' (I've seen this before).
'ma'+'stiff'='MASTIFF'
(Other definitions for mastiff that I've seen before include "Hound" , "Large short-haired dog breed" , "Big dog" , "Powerful dog breed" , "one of his best friends?" .)