The dogs start barking at the birds (7)
I believe the answer is:
beagles
'the dogs' is the definition.
(beagle is a kind of dog)
'at the birds' is the wordplay.
'at' becomes 'b' (I am not sure about this - if you are sure you should believe this answer much more).
'the birds' becomes 'eagles' (eagle is a kind of bird).
'b'+'eagles'='BEAGLES'
'start barking' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for beagles that I've seen before include "Dogs" , "Hunting hounds" , "These hounds bag eels badly" , "Short-legged hounds" .)