Dog makes mother tense (7)
I believe the answer is:
mastiff
'dog' is the definition.
(breed of dog)
'mother tense' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'tense' becomes 'stiff' (I am not sure about this - if you are sure you should believe this answer much more).
'ma'+'stiff'='MASTIFF'
'makes' acts as a link.
Can you help me to learn more?
(Other definitions for mastiff that I've seen before include "Powerful, smooth-coated dog used for security work" , "Large short-haired dog breed" , "Large, powerful, short-haired dog" , "Big dog" , "Powerful dog breed" .)