Mistake involving a flower (7)
I believe the answer is:
bloomer
I believe this is a double definition.
'mistake' is the first definition.
(thesaurus)
'a flower' is the second definition.
(I've seen this before)
'involving' acts as a link.
(Other definitions for bloomer that I've seen before include "rose, say" , "Loaf of bread" , "Big mistake" , "Crusty loaf" , "made by a baker" .)