The most common and most likely answer to this crossword clue is the 9 letter word ARMADILLO
I've seen this crossword clue in The Guardian
A
R
M
A
D
I
L
L
O
More clues leading to the result ARMADILLO
- Creature in a stream grabbing frantic duck
- I am a droll, peculiar creature
- Burrowing animal, or llama I'd cooked!
- Endangered species, cuckoo, drowned in a stream close to Rio
- Mammal frantic in a small stream with reduced oxygen
- Mutating mallard duck devours one animal
- I am a droll, outlandish creature
- Protected animal is disturbed in a brook beside duck
- Animal disturbed gorillaeating bananas
- Give guns to Rashid to bag large ordinary animal
Buddy explains!

The straight part
We know that "creature" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case creature = armadillo.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 ARMADILLO mean?
ARMADILLO noun- Any of the burrowing mammals covered with bony, jointed, protective plates, order Cingulata, found in the Americas, especially in South America.