It's so naive altering excuse (7)
I believe the answer is:
evasion
'excuse' is the definition.
(I've seen this before)
'it's so naive altering' is the wordplay.
'altering' is an anagram indicator.
'so'+'naive'='sonaive'
'sonaive' with letters rearranged gives 'EVASION'.
(Other definitions for evasion that I've seen before include "Hedging" , "The act of dodging the issue." , "Circumvention" , "Attempt to avoid the point of an argument" , "Prevarication" .)