Someone pestering a dog (7)
I believe the answer is:
harrier
'a dog' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for harrier that I've seen before include "may get on your back?" , "that flies!" , "jump jet" , "Short-winged hawk" , "Bird - dog - plane" .)