Digger finally departs from highway, leaving nothing behind (9)
I believe the answer is:
intestate
'leaving nothing behind' is the definition.
(intestate means failing to leave a will)
'digger finally departs from highway' is the wordplay.
I cannot quite understand how this works, but
'from' could be 'in' (I've seen this in other clues) and 'in' is present in the answer.
'highway' could be 'state' (state highway is a kind of highway) and 'state' is found within the answer.
The remaining letters 'te' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
(Other definitions for intestate that I've seen before include "Lacking a will" , "not prepared to leave" , "Dying without having made a will" , "not prepared to die" , "Not having planned to leave" .)