Mark takes an officer ahead (5)
I believe the answer is:
colon
'mark' is the definition.
(I know that colon is a type of punctuation)
'an officer ahead' is the wordplay.
'an officer' becomes 'col' (short for colonel).
'ahead' becomes 'on' (synonyms).
'col'+'on'='COLON'
'takes' acts as a link.
(Other definitions for colon that I've seen before include "City at the Caribbean entrance to the Panama Canal" , "Costa Rican currency" , "cut short dependency?" , "Part of the intestine - punctuation mark" , "Panamanian port" .)