The most common and most likely answer to this crossword clue is the 3 letter word GUT
I've seen this crossword clue in Independent
G
U
T
More clues leading to the result GUT
- Turning over towing vessel in a narrow strait
- Leaders of group using Telemann’s material for strings
- Natural pull, upwards
- Ted would be very disappointed with this paunch
- Food processor, where small vessel up-ended
- Instinctive reversal of leading vessel
- Devastate German for good
- Yank gets upset stomach
- Boat heads west in sort of canal
- Clean out natural gas producer!
Buddy explains!

The straight part
We know that "stomach" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stomach = gut.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 GUT mean?
GUT noun- The alimentary canal, especially the intestine.
- The abdomen of a person, especially one that is enlarged
- The intestines of an animal used to make strings of a tennis racket or violin, etc.
- A person's emotional, visceral self.
- A class that is not demanding or challenging.
- A narrow passage of water.
- The sac of silk taken from a silkworm when ready to spin its cocoon, for the purpose of drawing it out into a thread. When dry, it is exceedingly strong, and is used as the snood of a fishing line.
- To eviscerate.
- To remove or destroy the most important parts of.
- Made of gut.
- Instinctive.