Most unclean (8)
I believe the answer is:
dirtiest
'most unclean' is the definition.
('dirty' can be a synonym of 'unclean')
This is the entire clue.
(Other definitions for dirtiest that I've seen before include "Most filthy" , "Filthiest" , "Most obscene" , "Most unclean" , "Least clean" .)