A mark that you notice (4)
I believe the answer is:
spot
This clue might be a double definition.
'a mark that you' is the first definition.
'spot' can be an answer for 'a mark' (I've seen this before). I am unsure of the rest of the definition.
'notice' is the second definition.
(spot can mean to notice or observe)
Can you help me to learn more?
(Other definitions for spot that I've seen before include "Notice - stain - pick out" , "awkward situation" , "Sight - site" , "jam > stain" , "20 [MARK]" .)