The most common and most likely answer to this crossword clue is the 4 letter word WORM
I've seen this crossword clue in Financial Times
W
O
R
M
More clues leading to the result WORM
- Bait Mike put on end of line, twisting
- . Contemptible sort will argue back to Mark
- Staple item on the early bird menu?
- Shabby message from a happy early bird?
- Rotten food scoffed by new owner
- Decaying and exhausted, swallowing food, getting energy
- Old and tired argument overturned before workers accept serving of tea
- Old deteriorating watermelon left out
- Old, worn out description of cast?
- Barney returned money? That’s a fluke!
Buddy explains!

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 WORM mean?
WORM noun- A generally tubular invertebrate of the annelid phylum; an earthworm.
- More loosely, any of various tubular invertebrates resembling annelids but not closely related to them, such as velvet worms, acorn worms, flatworms, or roundworms.
- A type of wingless "dragon", especially a gigantic sea serpent.
- Either a mythical "dragon" (especially wingless), a gigantic sea serpent, or a creature that resembles a Mongolian death worm.
- A contemptible or devious being.
- A self-replicating program that propagates through a network.
- A graphical representation of the total runs scored in an innings.
- Anything helical, especially the thread of a screw.
- Any creeping or crawling animal, such as a snake, snail, or caterpillar.
- An internal tormentor; something that gnaws or afflicts one’s mind with remorse.
- A strip of linked tiles sharing parallel edges in a tiling.
- The lytta.
- (preceded by definite article) A dance, or dance move, in which the dancer lies on the floor and undulates the body horizontally thereby moving forwards.
- To make (one's way) with a crawling motion.
- To move with one's body dragging the ground.
- To work one's way by artful or devious means.
- To work (one's way or oneself) (into) gradually or slowly; to insinuate.
- To effect, remove, drive, draw, or the like, by slow and secret means; often followed by out.
- (in “worm out of”) To drag out of, to get information that someone is reluctant or unwilling to give (through artful or devious means or by pleading or asking repeatedly).
- To fill in the contlines of (a rope) before parcelling and serving.
- To deworm (an animal).
- To cut the worm, or lytta, from under the tongue of (a dog, etc.) for the purpose of checking a disposition to gnaw, and formerly supposed to guard against canine madness.
- To clean by means of a worm; to draw a wad or cartridge from, as a firearm.