Catches sight of marks (5)
I believe the answer is:
spots
I believe this is a double definition.
'catches sight of' is the first definition.
(spotting is a kind of catching sight of)
'marks' is the second definition.
(I know this)
(Other definitions for spots that I've seen before include "Acne" , "Picks out" , "Blemishes" , "Result of outbreak, possibly" , "Espies the blobs?" .)