Forfeit voluntarily
I believe the answer is:
waive
'forfeit voluntarily' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for waive that I've seen before include "Relinquish" , "Refrain from insisting on right or claim" , "Surrender" , "Refrain from insisting on rights" , "Not insist on (claim)" .)