Job of gun dog being derided (7,3,4)
I believe the answer is:
getting the bird
'job of gun dog' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'being derided' is the wordplay.
I cannot quite understand how this works, but
'being' could be 'bird' (bird is a kind of being) and 'bird' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for getting the bird that I've seen before include "Being hissed at" , "shopping for a goose?" , "Being booed" , "errand for Christmas cook?" .)