Robert has been ahead in Olympic event (7)
I believe the answer is:
bobsled
'olympic event' is the definition.
(I've seen this before)
'robert has been ahead in' is the wordplay.
'robert' becomes 'bob' (short for Robert).
'has' means one lot of letters go next to another.
'been' becomes 'led' (leading is a kind of being).
'ahead' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'in' indicates putting letters inside.
'bob'+'led'='bobled'
'bobled' placed around 's' is 'BOBSLED'.
(Another definition for bobsled that I've seen is " Olympic event".)