The most common and most likely answer to this crossword clue is the 4 letter word PIES
I've seen this crossword clue in Financial Times
P
I
E
S
Buddy explains!
The straight part
We know that "Anna/Anna/birds/birds" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case anna/anna/birds/birds = pies.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 PIES mean?
PIES verb- To spill or mix printing type.
- A type of pastry that consists of an outer crust and a filling.
- Any of various other, non-pastry dishes that maintain the general concept of a shell with a filling.
- (Northeastern US) A pizza.
- The whole of a wealth or resource, to be divided in parts.
- (letterpress) A disorderly mess of spilt type.
- An especially badly bowled ball.
- A pie chart.
- The vulva.
- To hit in the face with a pie, either for comic effect or as a means of protest (see also pieing).
- To go around (a corner) in a guarded manner.
- (of printing types) To reduce to confusion; to jumble.
- Magpie.
- The smallest unit of currency in South Asia, equivalent to 1/192 of a rupee or 1/12 of an anna.