The most common and most likely answer to this crossword clue is the 5 letter word YODEL
Y
O
D
E
L
More clues leading to the result YODEL
- Perform in meadow after climbing?
- Affectedly sing end of witty poem by Pound
- Sing version with new opening
- Sing in Tokyo, delightfully
- Sound made in Alps, intermittently, by loud bell
- Call when in range
- Solvers, almost, of the Spanish 15 style
- Hey Derek, make an off-peak call
- How the Swiss might call on Derek …
- An off-peak call?
Buddy explains!

The straight part
We know that "sing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sing = yodel.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 YODEL mean?
YODEL noun- A song incorporating yodelling.
- To sing (a song) in such a way that the voice fluctuates rapidly between the normal chest voice and falsetto.