Carol turned out in thin singlet (6,5)

I believe the answer is:

silent night

I'm a little stuck... Click here to teach me more about this clue!

'carol' is the definition.
(I've seen this before)

'turned out in thin singlet' is the wordplay.
'thin singlet' can be anagrammed to 'SILENT NIGHT'.
However, I am not clear how this is indicated.

Can you help me to learn more?

(Other definitions for silent night that I've seen before include "Blood sucking mammals" , "Christmas carol - hours of undisturbed sleep?" .)

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.