Unwashed food at hand (6)
I believe the answer is:
grubby
'unwashed' is the definition.
(I've seen this before)
'food at hand' is the wordplay.
'food' becomes 'grub' (grub is a kind of food).
'at hand' becomes 'by' (I can't justify this - if you can you should believe this answer much more).
'grub'+'by'='GRUBBY'
Can you help me to learn more?
(Other definitions for grubby that I've seen before include "Dirty or unwashed, as urchin may be" , "Dirty, grimy" , "Dirty, could do with with a wash" , "Squalid" , "Covered with ingrained dirt" .)