The most common and most likely answer to this crossword clue is the 5 letter word VIREO
V
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Buddy explains!
The straight part
We know that "bird" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bird = vireo.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does VIREO mean?
VIREO noun- Any of a number of small insectivorous passerine birds, of the genus Vireo, that have grey-green plumage.
- Any bird of the family Vireonidae, which includes vireos, shrike-vireo, greenlets and peppershrikes.
- (in plural) The family Vireonidae.