In study I messed up division (8)
I believe the answer is:
disunity
'division' is the definition.
(thesaurus)
'in study i messed up' is the wordplay.
'messed up' is an anagram indicator.
'in'+'study'+'i'='instudyi'
'instudyi' anagrammed gives 'DISUNITY'.
(Other definitions for disunity that I've seen before include "conflict" , "Lack of solidarity" , "Lack of oneness" , "Lack of agreement" .)