V-formation birds (5)
I believe the answer is:
geese
'v-formation birds' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for geese that I've seen before include "Domesticated birds" , "Water birds related to ducks and swans" , "Birds; silly people" , "Simpletons" , "Water birds; fools" .)