Part of flower showing black mark (6)
I believe the answer is:
stigma
I believe this is a double definition.
'part of flower' is the first definition.
(I know that stigma is part of style)
'black mark' is the second definition.
(I've seen this in another clue)
'showing' is the link.
(Other definitions for stigma that I've seen before include "Sign of disgrace" , "Mark of infamy or disgrace" , "Blot" , "part of plant" , "Disgraceful sign" .)