The most common and most likely answer to this crossword clue is the 3 letter word ELS
E
L
S
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 ELS mean?
ELS noun- The name of the Latin-script letter L.
- An elevated railway, especially for specific systems such as the metro in Chicago.
- The
- (used only with indefinite or interrogative pronouns) Other; in addition to previously mentioned items.