Holy cow, say, upheld as close to pure by pundit (3,4)
I believe the answer is:
gee whiz
'holy cow' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'upheld as close to pure by pundit' is the wordplay.
'upheld' is a reversal indicator.
'as' becomes 'eg' (I've seen this in other clues).
'close to' indicates one should take the final letters (the close/ending of).
'by pundit' becomes 'whiz' (I can't explain this - if you can you should believe this answer much more).
The final letter of 'pure' is 'e'.
'eg' written backwards gives 'ge'.
'ge'+'e'+'whiz'='GEE-WHIZ'
'say' acts as a link.
Can you help me to learn more?
(Other definitions for gee whiz that I've seen before include "Amazing" , "Exclamation of surprise (mainly US)" , "may accompany a gasp?" , "Expression of admiration" , "Interjection of surprise" .)