The most common and most likely answer to this crossword clue is the 3 letter word JAM
I've seen this crossword clue in Financial Times
J
A
M
Buddy explains!
The straight part
We know that "Preserve/stuff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case preserve/stuff = jam.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 JAM mean?
JAM noun- A sweet mixture of fruit boiled with sugar and allowed to congeal. Often spread on bread or toast or used in jam tarts.
- A difficult situation.
- Blockage, congestion.
- An informal, impromptu performance or rehearsal.
- (by extension) A song; a track.
- (by extension) An informal event where people brainstorm and collaborate on projects.
- To get something stuck in a confined space.
- To brusquely force something into a space; cram, squeeze.
- To cause congestion or blockage. Often used with "up"
- To block or confuse a broadcast signal.
- To throw a pitch at or near the batter's hands.
- To play music (especially improvisation as a group, or an informal unrehearsed session).
- To injure a finger or toe by sudden compression of the digit's tip.
- To attempt to score points.
- To bring (a vessel) so close to the wind that half her upper sails are laid aback.
- To give up on a date or some joint endeavour; stand up, chicken out, jam out.
- A kind of frock for children.
- (interior decorating) Either of the vertical components that form the side of an opening in a wall, such as that of a door frame, window frame, or fireplace.
- Any thick mass of rock that prevents miners from following the lode or vein.