Willingly dead? (7)
I believe the answer is:
testate
'willingly dead?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for testate that I've seen before include "Having made a legal will" , "Leaving a will" , "Having left valid will at death" , "With a legally valid will" , "Having made a last will and testament" .)