Mark and Stanley getting out of line (5)
I believe the answer is:
stain
'mark' is the definition.
(I know that mark can be written as stain)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for stain that I've seen before include "Smear" , "Discolour - blemish" , "Dirty mark; dye" , "Tarnish" , "Stigma" .)