Accepts without question certain birds (8)
I believe the answer is:
swallows
'accepts' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for swallows that I've seen before include "Birds with forked tails" , "Knocks back" , "migrants regularly taking flight" , "Takes in" , "Small migratory birds" .)