Telling lie Grant is found out (8)
I believe the answer is:
relating
'telling' is the definition.
(relating is a kind of telling)
'lie grant is found out' is the wordplay.
'is found out' indicates an anagram (discovered out of the normal letter order).
'lie'+'grant'='liegrant'
'liegrant' with letters rearranged gives 'RELATING'.
(Other definitions for relating that I've seen before include "Telling, narrating" , "Narrating, recounting" , "account" , "Connecting things in thought or meaning" , "Rendering" .)