Hesitation happening before rider (7)
I believe the answer is:
eventer
'rider' is the definition.
(I have seen 'Competitive rider ' mean 'eventer' so perhaps 'rider' could also mean 'eventer')
'hesitation happening before' is the wordplay.
'hesitation' becomes 'er' (sound made while hesitating - um, er).
'happening' becomes 'event' (I've seen this in other clues).
'before' is a charade indicator (letters next to each other).
'er' put after 'event' is 'EVENTER'.
(Other definitions for eventer that I've seen before include "Competitive horse/rider" , "Rider in contests" , "Competing horse or rider" , "versatile horse" , "Sportsman" .)