She set out treatises (6)
I believe the answer is:
theses
'treatises' is the definition.
(I know this)
'she set out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'she'+'set'='sheset'
'sheset' anagrammed gives 'THESES'.
(Other definitions for theses that I've seen before include "Essays on a theme" , "Premises" , "Degree dissertations" , "Academic dissertations" .)