Bird droppings over plaster walls (9)
I believe the answer is:
partridge
'bird' is the definition.
(I know that partridge is a type of wildfowl)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for partridge that I've seen before include "Flier" , "Peculiarly apt girder for the game bird" , "Game bird (in a pear tree?)" , "Widespread bird" , "1st" .)