Ancient Gaul's cut by daggers (5)
I believe the answer is:
obeli
'daggers' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for obeli that I've seen before include "Textual indicators" , "Dagger signs for footnotes" , "Little daggers" , "Signs referring to footnotes" , "Printers' marks; be oil (anag.)" .)