Obligate (6)
I believe the answer is:
compel
'obligate' is the definition.
(I know that obligate can be written as compel)
This is the entire clue.
(Other definitions for compel that I've seen before include "Urge on, force" , "Coerce, force to obey" , "Use force or influence to make something happen" , "Make someone do something" , "Use force or influence to make person do something" .)