The most common and most likely answer to this crossword clue is the 4 letter word KOHL
I've seen this crossword clue in Financial Times
K
O
H
L
Buddy explains!

The straight part
We know that "Something black" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case something black = kohl.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 KOHL mean?
KOHL noun- A dark powder (usually powdered antimony) used as eye makeup, especially in Eastern countries; stibnite.
- To decorate one's eyes with kohl.