It's good lie to confuse theoretician (10)
I believe the answer is:
ideologist
'theoretician' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'it's good lie to confuse' is the wordplay.
'to confuse' is an anagram indicator.
'its'+'good'+'lie'='itsgoodlie'
'itsgoodlie' anagrammed gives 'IDEOLOGIST'.
Can you help me to learn more?
(Other definitions for ideologist that I've seen before include "one theorizes grandly" , "Computer workstation" , "Supporter of political theory" , "Theorist, visionary" , "Political theorist" .)