Graduate introducing Holy Writ, not one for gibberish (6)
I believe the answer is:
babble
'gibberish' is the definition.
(babble is a kind of gibberish)
'graduate introducing holy writ not one' is the wordplay.
'graduate' becomes 'ba'.
'introducing' is a charade indicator (letters next to each other).
'holy writ' becomes 'bible' ('bible' can be a synonym of 'holy writ').
'not' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'bible' with 'i' taken out is 'bble'.
'ba'+'bble'='BABBLE'
'for' acts as a link.
(Other definitions for babble that I've seen before include "Region of S. Germany" , "Talk (like a brook?)" , "Utter gibberish" , "Rapid and incomprehensible talk" , "talk incessantly" .)