Wilberforce achieved this changing oil in boat (9)
I believe the answer is:
abolition
'wilberforce achieved this' is the definition.
The definition suggests a singular noun which matches the answer.
'changing oil in boat' is the wordplay.
'changing' indicates anagramming the letters.
'oil'+'in'+'boat'='oilinboat'
'oilinboat' with letters rearranged gives 'ABOLITION'.
Can you help me to learn more?
(Other definitions for abolition that I've seen before include "Eradication" , "Action of doing away with something" , "Act of putting an end to something" , "Annulment" , "Wilberforce achieved it" .)