Perhaps mistaking ink mark? (6)
I believe the answer is:
stigma
'mark?' is the definition.
('stigma' can be a synonym of 'mark')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stigma that I've seen before include "Mark of shame or social disgrace" , "Blot" , "Brand or mark of infamy" , "Sign of disgrace" , "Disgraceful sign" .)