The most common and most likely answer to this crossword clue is the 4 letter word POOP
I've seen this crossword clue in The Guardian
P
O
O
P
More clues leading to the result POOP
Buddy explains!

The straight part
We know that "Feature of stern" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case feature of stern = poop.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 POOP mean?
POOP noun- Fecal matter, feces.
- The sound of a steam engine's whistle; typically low pitch.
- To make a short blast on a horn
- To break wind.
- To defecate.
- A set of data or general information, written or spoken, usually concerning machinery or a process.
- To tire, exhaust. Often used with out.
- The stern of a ship.
- The poop deck.
- To break seawater with the poop of a vessel, especially the poop deck.
- To embark a ship over the stern.
- A slothful person.