Jockey exaggerated jumps during clumsy ride (7)
I believe the answer is:
dettori
'jockey' is the definition.
(jockey Frankie Dettori)
'exaggerated jumps during clumsy ride' is the wordplay.
'exaggerated' becomes 'OTT' (short for 'over the top').
'jumps' shows that the letters should be reversed in order (I've seen 'jumping' mean this (in a down clue, letters jump up)).
'during' indicates putting letters inside.
'clumsy' indicates anagramming the letters.
'ott' in reverse letter order is 'tto'.
'ride' with letters rearranged gives 'deri'.
'tto' going within 'deri' is 'DETTORI'.
(Another definition for dettori that I've seen is " Jockey".)