Ink mishap (5)
I believe the answer is:
smear
'ink mishap' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for smear that I've seen before include "Greasy/sticky mark" , "Slanderous denigration of character" , "Unwarranted accusation" , "False accusation; blur" , "False report" .)