Note penetrating conclusion is correct (5)
I believe the answer is:
'is correct' is the definition.
'note penetrating conclusion' is the wordplay.
'note' becomes 'me' (**).
'penetrating' is an insertion indicator.
'conclusion' becomes 'end' (end is a kind of conclusion).
'me' put inside 'end' is 'EMEND'.
(Other definitions for emend that I've seen before include "Correct, revise (text)" , "Alter to improve (text)" , "change" , "do editorial work" , "Make improvements to (text)" .)