Mark at two points? (5)
I believe the answer is:
colon
I believe this clue is a double definition.
'mark' is the first definition.
(colon is a kind of punctuation mark)
'two points?' is the second definition.
(I've seen this in another clue)
'at' acts as a link.
(Other definitions for colon that I've seen before include ": - bit of the gut" , "City at the Caribbean entrance to the Panama Canal" , "Part of the intestine - punctuation mark" , "Start of one canal" , "Part of body; some punctuation" .)