Spreading dirt about coppers is a damaging thing to do (5)
I believe the answer is:
spoil
'a damaging thing to do' is the definition.
I can't tell whether this definition defines the answer.
'spreading dirt about coppers' is the wordplay.
'spreading dirt' becomes 'soil' (synonyms. I am not sure about the 'spreading' bit.).
'about' indicates putting letters inside.
'coppers' becomes 'p'.
'soil' placed around 'p' is 'SPOIL'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for spoil that I've seen before include "Harm or destroy" , "Treat overindulgently" , "Cook" , "Deface" , "Booty" .)