Narrate story that’s revealing (8)
I believe the answer is:
telltale
'revealing' is the definition.
('telltale' can be a synonym of 'revealing')
'narrate story' is the wordplay.
'narrate' becomes 'tell' ('tell' can be a synonym of 'narrate').
'story' becomes 'tale' ('tale' can be a synonym of 'story').
'tell'+'tale'='TELLTALE'
'that's' acts as a link.
(Other definitions for telltale that I've seen before include "One revealing secrets" , "Gossip-monger" , "Revealing or indicating something, like blabbermouth" , "Person who blabs, or something revealing" , "Blabbermouth, snitch" .)