Soften, with "down" (4)
I believe the answer is:
tone
'soften with down' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tone that I've seen before include "Musical sound of note" , "Note; note (anag.)" , "Theobald Wolf . . . ." , "Vocal sound of note" , "Sound - style" .)