Start writing notes out (5)
I believe the answer is:
onset
'start' is the definition.
(both can mean the beginning of something)
'notes out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'notes' anagrammed gives 'ONSET'.
'writing' acts as a link.
(Other definitions for onset that I've seen before include "Beginning; violent attack" , "Start - opening moments" , "Attack using stone" , "Beginning (of disease etc)" , "Appearance of" .)