The most common and most likely answer to this crossword clue is the 3 letter word SEN
I've seen this crossword clue in The Guardian
S
E
N
More clues leading to the result SEN
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 SEN mean?
SEN noun- A unit of Japanese currency, worth one hundredth of a yen.
- A coin of this value.
- Self
- A unit of length equal 20 wa, 40 meters