Make a solemn pledge or promise (3)
I believe the answer is:
vow
(Other definitions for vow that I've seen before include "Oath or solemn promise" , "Promise, swear" , "Pledge, take oath" , "Binding promise" , "Solemn pledge" .)
I believe the answer is:
vow
(Other definitions for vow that I've seen before include "Oath or solemn promise" , "Promise, swear" , "Pledge, take oath" , "Binding promise" , "Solemn pledge" .)