Opposed to docking the tail, one says (5)
I believe the answer is:
avers
'says' is the definition.
('aver' can be a synonym of 'say')
'opposed to docking the tail one' is the wordplay.
I cannot really understand how this works, but
'opposed' could be 'v' (abbreviation for versus) and 'v' is found in the answer.
'one' could be 'a' (a thing is one thing) and 'a' is found in the answer.
The remaining letters 'ers' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for avers that I've seen before include "States to be true" , "States firmly - really raves" , "Alleges, asserts" , "States positively" , "Declares to be true" .)