So naive about avoidance (7)
I believe the answer is:
evasion
'avoidance' is the definition.
(I've seen this in another clue)
'so naive about' is the wordplay.
'about' is an anagram indicator.
'so'+'naive'='sonaive'
'sonaive' is an anagram of 'EVASION'.
(Other definitions for evasion that I've seen before include "A dodgy answer or excuse" , "Illegal avoidance (of tax)" , "Cunning" , "The act of dodging the issue." , "Circumvention" .)