The point of punctuation (4,4)
I believe the answer is:
full stop
I believe this clue is a double definition.
'the point' is the first definition.
('full stop' can be a synonym of 'point')
'punctuation' is the second definition.
(full stop is a kind of punctuation)
'of' is the link.
(Other definitions for full stop that I've seen before include "Point" , "period in America" , "Period of sentence" , "A period in the US!" , "'Punctuation mark (4,4)'" .)