The most common and most likely answer to this crossword clue is the 8 letter word BESTIARY
I've seen this crossword clue in The Times
B
E
S
T
I
A
R
Y
More clues leading to the result BESTIARY
- Prime journal, not the first treatise on animals
- Choice reflected your excellent work with animals
- Finest engagement book, not the first one featuring animals
- Supreme personal account, but not the original old book
- Work with animals in top aviary – not average
- Get going about a yellow book on animals
- Finest daily record— old book of animals
Buddy explains!

The straight part
We know that "one featuring animals" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one featuring animals = bestiary.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 BESTIARY mean?
BESTIARY noun- A medieval treatise of various real or imaginary animals.