Fine dirt (4)
I believe the answer is:
dust
'fine dirt' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for dust that I've seen before include "Unwanted fine powder" , "Powdered matter" , "Clean; fine powder" , "Do some housework - we all come to it!" , "Sprinkle -- powder" .)