Excelled with way to crack homework: cheating! (10)
I believe the answer is:
dishonesty
'cheating' is the definition.
(thesaurus)
'excelled with way to crack homework' is the wordplay.
'excelled' becomes 'shone' (shine can mean to excel or do well).
'with' means one lot of letters go next to another.
'way' becomes 'st' (abbreviation for street).
'to crack' indicates putting letters inside (inserted letters crack into others).
'homework' becomes 'diy' (DIY is work done on your home).
'shone'+'st'='shonest'
'shonest' inserted inside 'diy' is 'DISHONESTY'.
(Other definitions for dishonesty that I've seen before include "Graft" , "Untrustworthiness, insincerity" , "Bad behaviour" , "Crookedness" , "fraud" .)