Bit of a bloomer after Home Secretary's A&E mix-up (5)
I believe the answer is:
petal
'bit of a bloomer' is the definition.
(part of a flower, something which blooms)
I cannot understand how the rest of the clue works.
(Other definitions for petal that I've seen before include "One piece of corolla" , "Floral segment" , "Bit of blooming" , "Colourful flower part" , "A bit of flower" .)