Irresponsible act of Nero, supposedly cheating (8)
I believe the answer is:
fiddling
I believe this is a double definition.
'irresponsible act of nero supposedly' is the first definition.
(Nero supposedly fiddled while Rome burned)
'cheating' is the second definition.
(fiddle can mean to cheat or con)
(Other definitions for fiddling that I've seen before include "Such swindles may be" , "petty" , "trivial" , "wasting time?" , "Cooking the books" .)