Mother gets body of a dog (7)
I believe the answer is:
mastiff
'dog' is the definition.
(breed of dog)
'mother gets body' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'gets' says to put letters next to each other.
'body' becomes 'stiff' (stiff is a kind of body).
'ma'+'stiff'='MASTIFF'
'of a' acts as a link.
(Other definitions for mastiff that I've seen before include "Powerful breed of watchdog" , "Large short-haired dog breed" , "one of his best friends?" , "Big dog" , "Powerful, smooth-coated dog used for security work" .)