Choir messed up note - that's a bloomer (6)
I believe the answer is:
orchid
'a bloomer' is the definition.
(orchid is a kind of flowering plant)
'choir messed up note' is the wordplay.
'messed up' is an anagram indicator.
'note' becomes 'd' (musical note**).
'choir' anagrammed gives 'orchi'.
'orchi'+'d'='ORCHID'
'that's' is the link.
(Other definitions for orchid that I've seen before include "Ornate flower" , "Lush and expensive tropical flower" , "Exotic and expensive flower" , "Tropical flowering plant" , "lady's slipper, perhaps" .)