The most common and most likely answer to this crossword clue is the 4 letter word CROC
I've seen this crossword clue in The Guardian
C
R
O
C
More clues leading to the result CROC
- Tailless bird caught small reptile
- Reflective piece of music:: short snappy one
- Invalid said to be a fearsome swimmer
- Dangerous reptile about to top fabulous bird
- Swamp creature caught by enormous bird
- Invalid reported danger in river
- Pot, we hear, animal with valuable skin
- Beast, decrepit one, losing tail
- Well-ordered pupils bloom without us
- We leave a plant for a reptile
Buddy explains!

The straight part
We know that "animal with valuable skin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case animal with valuable skin = croc.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 CROC mean?
CROC noun- A crocodile.
- A plastic slip-on shoe.