Lacking will, hitch-hiker finally abandons US highway (9)
I believe the answer is:
intestate
'lacking will' is the definition.
'hitch-hiker finally abandons us highway' is the wordplay.
I cannot really see how this works, but
'highway' could be 'state' (state highway is a kind of highway) and 'state' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for intestate that I've seen before include "Passing on without leaving a will" , "not prepared to die" , "Lacking a will" , "Undecided about who should inherit" , "not prepared to leave" .)