As a standard of perfection it's varied by a non-practical type (8)
I believe the answer is:
idealist
'as' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'a standard of perfection it's varied by a non-practical type' is the wordplay.
'a standard of perfection' becomes 'ideal' (I've seen this in another clue).
'varied' is an anagram indicator.
'by' means one lot of letters go next to another.
'a non practical type' becomes 'i' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ts' with letters rearranged gives 'st'.
'st' after 'i' is 'ist'.
'ideal'+'ist'='IDEALIST'
Can you help me to learn more?
(Other definitions for idealist that I've seen before include "man of principle" , "Person with noble aspirations, perhaps unrealistic" , "An optimist or romantic" , "Person with lofty and unselfish aspirations" , "Hopeful type" .)