The most common and most likely answer to this crossword clue is the 5 letter word FLUKE
I've seen this crossword clue in The Guardian
F
L
U
K
E
More clues leading to the result FLUKE
- Accidental success bringing leader of felons to book
- Cause of liver rot initially foxed physician
- Kidney potato? 5 I have briefly left out, not very hot
- Worm‘s bit of good luck
- Lucky thing, a sucker
- Fine before 6 of the 26 flounder
- Worm, lucky thing
- Anchor bit parasite
- After Friday, Luke gets a piece of tail?
- Odd situation: Nick s rear caught in chimney passage
Buddy explains!

The straight part
We know that "Worm/bit of good luck" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case worm/bit of good luck = fluke.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 FLUKE mean?
FLUKE noun- A lucky or improbable occurrence, with the implication that the occurrence could not be repeated.
- To obtain a successful outcome by pure chance.
- To fortuitously pot a ball in an unintended way.
- A flounder.
- A trematode; a parasitic flatworm of the Trematoda class, related to the tapeworm.
- Either of the two lobes of a whale's or similar creature's tail.
- Any of the triangular blades at the end of an anchor, designed to catch the ground.
- A metal hook on the head of certain staff weapons (such as a bill), made in various forms depending on function, whether used for grappling or to penetrate armour when swung at an opponent.
- In general, a winglike formation on a central piece.
- Waste cotton.