Medium chance, without initial dirt (4)
I believe the answer is:
muck
'dirt' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for muck that I've seen before include "Dirt (associated with brass)" , "Farmyard manure" , "Dirt, manure" , "Dirt, mud" , "Moist farmyard dung" .)