Runner allowed in wash after start (7)
I believe the answer is:
athlete
'runner' is the definition.
(I've seen this in another clue)
'allowed in wash after start' is the wordplay.
'allowed' becomes 'let' (to let is to allow or permit).
'in' means one lot of letters goes inside another.
'wash' becomes 'bathe' (I've seen this before).
'after start' means to remove the first letter (I've seen 'after starting' mean this (only the letters found after the first are used)).
'bathe' with its first letter taken away is 'athe'.
'let' placed within 'athe' is 'ATHLETE'.
(Other definitions for athlete that I've seen before include "gymnast, perhaps" , "Runner, jumper, thrower" , "One competes in sports" , "Person trained to compete in sports" , "Jumper, say" .)