The most common and most likely answer to this crossword clue is the 4 letter word ARIA
A
R
I
A
More clues leading to the result ARIA
- A song coming up, one from an opera
- Song musician at first cut from role in West Side Story
- First-class article about Mahler's last song
- Song recalled in Hair, Aquarius
- A long number of answers, including right one
- Part of Rastafarian song
- Song from Callas, perhaps needing no introduction
- Song of heretical nationalist being rejected
- Opera song from Farrar I adored
- Song from opera or a show coming up
Buddy explains!

The straight part
We know that "Song from opera" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case song from opera = aria.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 ARIA mean?
ARIA noun- A musical piece written typically for a solo voice with orchestral accompaniment in an opera or cantata.