The most common and most likely answer to this crossword clue is the 8 letter word THROSTLE
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Buddy explains!

The straight part
We know that "Singer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case singer = throstle.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 THROSTLE mean?
THROSTLE noun- A song thrush.
- A machine for spinning wool, cotton, etc., from the rove, consisting of a set of drawing rollers with bobbins and flyers, and differing from the mule in having the twisting apparatus stationary and the processes continuous.