Peach stone brought to athlete missing start (7)
I believe the answer is:
stunner
'peach' is the definition.
(I know that peach can be written as stunner)
'stone brought to athlete missing start' is the wordplay.
'stone' becomes 'st'.
'brought to' says to put letters next to each other.
'athlete' becomes 'runner' (type of athlete).
'missing start' means to remove the first letter.
'runner' with its first letter removed is 'unner'.
'st'+'unner'='STUNNER'
(Other definitions for stunner that I've seen before include "Peach" , "Dish" , "Attractive person" , "Beauty (informal)" , "Good-looker (informal)" .)