Untidy person with a bit of a neck (6)
I believe the answer is:
scruff
This clue is a double definition.
'untidy person' is the first definition.
(I've seen this before)
'a bit of a neck' is the second definition.
('scruff' is part of 'neck')
'with' is the link.
(Other definitions for scruff that I've seen before include "One hardly washing" , "Tramp" , "bit of neck?" , "Back of the neck, used to lift cat" , "Part of neck" .)