He's willing to let others succeed (8)
I believe the answer is:
testator
'he's willing' is the definition.
(I've seen this before)
'to let others succeed' is the wordplay.
I cannot really see how this works, but
'to' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for testator that I've seen before include "One willing" , "A man who has made a will" , "He's willing" , "Will signatory" , "Will provider" .)