The most common and most likely answer to this crossword clue is the 6 letter word GOPHER
I've seen this crossword clue in Financial Times
G
O
P
H
E
R
Buddy explains!

The straight part
We know that "a small animal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a small animal = gopher.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 GOPHER mean?
GOPHER noun- A small burrowing rodent, especially in the family Geomyidae.
- The gopher tortoise.
- The gopher rockfish.
- A worker who runs errands; an errand boy.