The most common and most likely answer to this crossword clue is the 3 letter word PIG
I've seen this crossword clue in Financial Times
P
I
G
More clues leading to the result PIG
- Drop litter and stuff
- Old blockhead and general staff seen in photo in the old days
- Difficult problem: irrational number applied to gravitational measure
- By George, Napoleon is spying intermittently
- Perhaps Babe’s heart goes to hunter of boar
- Something very difficult in 12?
- Animal good with Indian boy cast adrift
- Plant zoo animal in den?
- One scoffs at one involved in film classification
- Creature emerging occasionally in spring
Buddy explains!

The straight part
We know that "By George, Napoleon" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case by george, napoleon = pig.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 PIG mean?
PIG noun- Any of several intelligent mammalian species of the genus Sus, having cloven hooves, bristles and a nose adapted for digging; especially the domesticated animal Sus scrofa.
- (specifically) A young swine, a piglet (contrasted with a hog, an adult swine).
- The edible meat of such an animal; pork.
- A light pinkish-red colour, like that of a pig (also called pig pink).
- Someone who overeats or eats rapidly and noisily.
- A lecherous or sexist man.
- A dirty or slovenly person.
- A very obese person.
- A police officer.
- A difficult problem.
- A block of cast metal.
- The mold in which a block of metal is cast.
- A device for cleaning or inspecting the inside of an oil or gas pipeline, or for separating different substances within the pipeline. Named for the pig-like squealing noise made by their progress.
- The general-purpose M60 machine gun, considered to be heavy and bulky.
- A simple dice game in which players roll the dice as many times as they like, either accumulating a greater score or losing previous points gained.
- (of swine) to give birth.
- To greedily consume (especially food).
- To huddle or lie together like pigs, in one bed.
- To clean (a pipeline) using a pig (the device).
- Earthenware, or an earthenware shard
- An earthenware hot-water jar to warm a bed; a stone bed warmer