Go back over event, after others lose son (7)
I believe the answer is:
retrace
'go back over' is the definition.
(thesaurus)
'event after others lose son' is the wordplay.
'event' becomes 'race' (race is a kind of event).
'after' is a charade indicator (letters next to each other).
'others' becomes 'rest' (eg the rest of a group).
'lose' indicates named letters should be taken away.
'son' becomes 's' (genealogical abbreviation for son).
'rest' with 's' taken away is 'ret'.
'race' put after 'ret' is 'RETRACE'.
(Another definition for retrace that I've seen is " Go back over (one's steps)".)