TV show judge's entertaining pooch? (7)
I believe the answer is:
terrier
'pooch?' is the definition.
(type of dog)
'tv show judge's entertaining' is the wordplay.
'tv show' becomes 'ER' (US medical drama).
'judge' becomes 'trier' (a judge tries a case in court).
'entertaining' is an insertion indicator.
'er' going within 'trier' is 'TERRIER'.
(Other definitions for terrier that I've seen before include "Small, originally burrowing, dog" , "Sealyham, for example" , "One who volunteers to fight" , "Dog - army volunteer - land register" , "Persistent person" .)