No quote stands up as purely intellectual (6)
I believe the answer is:
noetic
'purely intellectual' is the definition.
(noetic means relating to the intellect)
'no quote stands up' is the wordplay.
'quote' becomes 'cite' (synonyms).
'stands up' is a reversal indicator (I've seen 'stand up' mean this (in a down clue, the word stands upside down)).
'cite' in reverse letter order is 'etic'.
'no'+'etic'='NOETIC'
'as' acts as a link.
(Other definitions for noetic that I've seen before include "Of a mind" , "Intellectual" , "Relating to the intellect" .)