Old road and river dropping? (6)
I believe the answer is:
ordure
'dropping?' is the definition.
'old road and river' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'road' becomes 'rd' (abbreviation).
'and' means one lot of letters go next to another.
'river' becomes 'ure' (river in Yorkshire).
'o'+'rd'+'ure'='ORDURE'
(Other definitions for ordure that I've seen before include "soil" , "Dirt" , "Excrement" , "Dung, filth" , "unclean" .)