Upright member on internet surprisingly rude (11)
I believe the answer is:
impertinent
'rude' is the definition.
(I've seen this in another clue)
'upright member on internet surprisingly' is the wordplay.
'upright member' becomes 'imp' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'surprisingly' indicates an anagram (a surprising ordering of the letters).
'internet' is an anagram of 'ertinent'.
'imp'+'ertinent'='IMPERTINENT'
Can you help me to learn more?
(Other definitions for impertinent that I've seen before include "Saucy" , "Rude" , "Disrespectful" , "Showing little respect" , "Bold" .)