Mother with wooden dog (7)
I believe the answer is:
mastiff
'dog' is the definition.
(breed of dog)
'mother with wooden' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'with' means one lot of letters go next to another.
'wooden' becomes 'stiff' (as in wooden acting).
'ma'+'stiff'='MASTIFF'
(Other definitions for mastiff that I've seen before include "one of his best friends?" , "Large, powerful, short-haired dog" , "Powerful dog breed" , "Large short-haired dog breed" , "Hound" .)