Leave detailed incantation in sacred text (6)
I believe the answer is:
gospel
'sacred text' is the definition.
(I know that Gospel is a type of sacred text)
'leave detailed incantation' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'detailed' means to remove the last letter (the tail of the word is removed).
'incantation' becomes 'spell' (I've seen this in another clue).
'spell' with its final letter taken away is 'spel'.
'go'+'spel'='GOSPEL'
'in' acts as a link.
(Other definitions for gospel that I've seen before include "Type of music" , "One of the first four Books of the New Testament" , "Truth (religious)" , "Unquestionable truth - church doctrine" , "Black evangelical singing" .)