Dad's hunch about dog (9)
I believe the answer is:
dachshund
'dog' is the definition.
(I know that Dachshund is a type of dog)
'dad's hunch about' is the wordplay.
'about' indicates an anagram.
'dads'+'hunch'='dadshunch'
'dadshunch' anagrammed gives 'DACHSHUND'.
(Other definitions for dachshund that I've seen before include "low-down dog" , "Dad's hunch about the dog" , "Long, low dog" , "Small dog (from Germany?)" , "Long-bodied, short-legged breed of dog" .)