One willing to try schedule after turning back (8)
I believe the answer is:
testator
'one willing' is the definition.
(person making a will)
'try schedule after turning back' is the wordplay.
'try' becomes 'test' (test is a kind of try).
'schedule' becomes 'rota' (I've seen this before).
'after turning back' shows that the letters should be reversed in order.
'rota' backwards is 'ator'.
'test'+'ator'='TESTATOR'
'to' acts as a link.
(Other definitions for testator that I've seen before include "Person who makes a will" , "He's willing" , "Will compiler" , "A man who has made a will" , "Will producer" .)