The most common and most likely answer to this crossword clue is the 8 letter word NEMATODE
I've seen this crossword clue in The Daily Telegraph
N
E
M
A
T
O
D
E
More clues leading to the result NEMATODE
- The last word about warty amphibian, we hear, or worm
- Junction blocked by return of pet worm
- Demon ate wriggly worm
- Worm, harmless coiling round, getting into knot
- It’s tricky to demean a worm
- Worm that turned flat in bud
- Worm has name confused with toad, we hear
- Worm crossing over oriental carpet
- Treated one, made to remove ringworm
Buddy explains!

The straight part
We know that "a worm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a worm = nematode.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 NEMATODE mean?
NEMATODE noun- A worm of the large phylum Nematoda, such as a roundworm or threadworm.