The punctuation, pass over (5)
I believe the answer is:
colon
'the punctuation' is the definition.
(colon is a kind of punctuation)
'pass over' is the wordplay.
'pass' becomes 'col' (col is a term for a mountain pass).
'over' becomes 'on' (physically on top of).
'col'+'on'='COLON'
(Other definitions for colon that I've seen before include "Panamanian port" , "Costa Rican currency" , "Punctuate part of the large intestine" , "Stop (on the inside!)" , "Stop (less than full)" .)