Smarty-pants says no and everyone follows (4-3)
I believe the answer is:
know-all
'smarty-pants' is the definition.
(I've seen this before)
'says no and everyone follows' is the wordplay.
I cannot really understand how this works, but
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is present in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found within the answer.
'everyone' could be 'all' (all people) and 'all' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for know-all that I've seen before include "One supposedly omniscient" , "Person who thinks he has all the answers" , "Self-styled polymath" , "Smart Aleck" , "Pedantic" .)