Soprano instantly discards bloomers in winter (9)
I believe the answer is:
snowdrops
'bloomers in winter' is the definition.
(winter flowers)
'soprano instantly discards' is the wordplay.
'soprano' becomes 's' (musical abbreviation).
'instantly' becomes 'now'.
'discards' becomes 'drops'.
's'+'now'+'drops'='SNOWDROPS'
(Other definitions for snowdrops that I've seen before include "Avalanches" , "flowers" .)