Narrating is informative (7)
I believe the answer is:
telling
This clue is a double definition.
'narrating' is the first definition.
('tell' can be a synonym of 'narrate')
'informative' is the second definition.
(similar in meaning)
'is' is the link.
(Other definitions for telling that I've seen before include "of significance" , "Counting" , "Effective - narration" , "Powerful; informing" , "influential" .)