Marks that upset good men (6)
I believe the answer is:
stains
'marks' is the definition.
(I know this)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stains that I've seen before include "Sullies" , "Discolorations on satins" , "Discolours or dyes wood" , "Discolourations on satins" , "Discolorations or dirt marks" .)