The most common and most likely answer to this crossword clue is the 7 letter word KESTREL
I've seen this crossword clue in Independent
K
E
S
T
R
E
L
More clues leading to the result KESTREL
- Raptor’s way to get into vessel crossing river
- Flier, quickest, relative displays
- Bird entering weakest relationship
- Small falcon among quickest released
- Bird that’s seen in new trees planted in centre of Auckland
- Twisting, unending street in Kabul’s outskirts, home to bird of prey
- Bird’s wet bottom bearing half of strain
- Flier, leading light after one’s gone in part of ship
- In part of Hull on vacation, spot river bird
- Bird among quickest released
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 = kestrel.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 KESTREL mean?
KESTREL noun- Any of various small falcons of the genus Falco that hover while hunting.
- The common kestrel, Falco tinnunculus.