In the end dog will bite them to pay them back for their annoying barking (7)
I believe the answer is:
yapping
'barking' is the definition.
(yapping is a kind of barking)
'in the end dog will bite them to pay them back for their annoying' is the wordplay.
I cannot quite see how this works, but
'in' is found in the answer.
an anagram of 'pay' is 'yap' which is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for yapping that I've seen before include "Dog's noise" , "Barking like a small dog or chatting" .)