Go on telling you what's been happening (5,4)
'go on' is the definition.
(resuming is a kind of going on)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for resume that I've seen before include "Abstract" , "Begin activity again" , "American CV" , "Continue after a break" , "list of achievements in Washington?" .)
'go on telling you what's been' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'happening' is the wordplay.
I cannot quite see how this works, but
'happening' could be 'time' (time is a kind of happening) and 'time' is located in the answer.
The remaining letters 'marks' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?