Cartoon character frames mischievous graph (3,5)
I believe the answer is:
bar chart
'graph' is the definition.
(type of graph)
'cartoon character frames mischievous' is the wordplay.
'cartoon character' becomes 'Bart' (Bart Simpson from The Simpsons).
'frames' means one lot of letters goes inside another.
'mischievous' becomes 'arch' (arch can mean mischievous or playful).
'bart' enclosing 'arch' is 'BAR-CHART'.
(Other definitions for bar chart that I've seen before include "display of information" , "Diagram showing figures" , "graph" , "Table" .)