Outline problem ahead (3,2)
I believe the answer is:
sum up
'outline' is the definition.
(outline can mean to sum up or summarise)
'problem ahead' is the wordplay.
'problem' becomes 'sum' (arithmetic problem).
'ahead' becomes 'up' (similar in meaning).
'sum'+'up'='SUM UP'
(Other definitions for sum up that I've seen before include "Review evidence at end of a case" , "(Of a judge) review the evidence" , "Provide a synopsis" , "What a judge may do" , "Of a judge, give the main points of the evidence for jury" .)